Option Pricing via Risk-Neutral Density Forecasting Stanislav Khrapov∗ New Economic School September 15, 2014 Abstract We propose a novel approach to option pricing. It exploits strong predictability in option-implied risk-neutral densities. To illustrate the idea we use a mixture of log-normal and a generalized beta as the candidates for the distribution of underlying stock price under the risk-neutral measure. Using the closed-form solutions for option prices we extract risk-neutral densities and forecast them one week ahead. This forecast allows to compute one week ahead option prices and compare them to the observables. In the empirical exercise we show that the option pricing performance is on par with state-of-the-art stochastic volatility models. Keywords: risk-neutral density, option pricing, forecasting JEL Classification: C58, G13, G17 ∗ Address: New Economic School, Nakhimovskiy Prospekt 47, Moscow, Russia, 117418. Phone: +7 (495) 956 9508. Email: [email protected] 1 Introduction Black & Scholes (1973) have opened the whole new chapter in the history of quantitative finance. The field of option pricing has started with this seminal paper. Since then the option pricing error has become the holy grail for the plethora of financial economists. State-of-the-art option pricing models include Heston & Nandi (2000), Christoffersen et al. (2006, 2008, 2009), Corsi et al. (2013), and Majewski et al. (2013) among many others. In this paper we propose a novel approach to option pricing which even in its simplest form preforms close to above mentioned models in terms or reducing option pricing errors. The main idea of the model is based on predictability of option-implied risk-neutral density. Our paper is related to the literature on option-implied information, including risk-neutral densities and implied volatility surfaces (see Christoffersen et al. (2012a) for a comprehensive overview of the field, or Jackwerth (2004) for an earlier survey). The standard approach to option pricing nowadays is through the no-arbitrage argument. It simply says that the options are the expectations under the risk-neutral distribution of the future payoff which in the case of call contract is (S − K)+ . This definition reveals the key to extraction of the risk-neutral density of the underlying. For example, Ait-Sahalia & Lo (1998) extract this density non-parametrically, while Bahra (1996, 1997) do it assuming parametric form of the density. Other examples include Söderlind & Svensson (1997), Melik & Thomas (1997), Jondeau & Rockinger (2000), Jackwerth (2004), Bu & Hadri (2007), and Figlewski (2010). In particular, we use the approach taken by Bahra (1996, 1997) to extract parameters of the mixture of log-normal distributions from the cross-section of option prices available on any trading day. Then we find that these densities are in fact highly predictable. These predictability patterns allow us to forecast densities one week ahead and use these forecasts to compute model option prices and volatility surfaces. Another strand of literature related to our paper is on predictability in the space of implied volatilities. Option prices are most often quoted in terms of Black-Scholes implied volatilities. The benefit of doing so is that option prices can then be compared across strikes, maturities, and price levels of the underlying. It turns out that the volatility surface is also highly predictable across time. Among papers that observe such predictability in different settings are Dumas et al. (1998), Cont & da Fonseca (2002), Gonçalves & Guidolin (2006), Fengler et al. (2007), and Homescu (2011). Note that volatility surface is just a monotone transformation of the option prices. So it becomes another side of a single big picture, along with risk-neutral density, which says that option-implied information is persistent. In this paper we exploit this information for the purposes of option pricing. To be more specific we do the following. First, similarly to Bahra (1996), Melik & Thomas (1997), and Söderlind & Svensson (1997), we assume that the stock price under the risk-neutral measure is distributed as a mixture of log-normal distributions. In particular, this model encompasses geometric Brownian motion as a special case which makes it our empirical benchmark. Next, we use the theoretical result that gives us closed-form solutions to option prices that depend only on a few parameters. The mixture of log-normals is very attractive since it produces asymmetry and 2 fatter tails which is a minimal requirement for successful option pricing model. Similarly to Liu et al. (2007) we also try the Generalized Beta distribution with some modification relative to the original in order to make this distribution parameters horizon invariant. Given a cross-section of daily option prices we find the risk-neutral densities, or equivalently the set of parameters, that minimize the option pricing errors. This exercise is repeated every day to collect the time series of density parameters. It turns out that these parameters are highly predictable. We exploit this predictability by fitting a simplest autoregressive model to each series of parameters. Then, we forecast these parameters out-of-sample and compute option prices corresponding to the forecast of the risk-neutral density. Our empirical analysis shows that this approach produces uniformly small option pricing errors across moneyness, maturities, and across time. The rest of the paper is organized as follows. Section 2 introduces the model for option prices based on the mixture of log-normal risk-neutral densities of the underlying stock price. Section 3 develops the methodology to extract the risk-neutral densities, forecast them, and use the forecast to compute model option prices. Section 4 describes the data and empirical results. Section 5 concludes. 2 The Model 2.1 Motivation We begin this section with a very simplistic set up used in the seminal work of Black & Scholes (1973). Suppose that under the risk-neutral measure the stock price ST evolves according to the geometric Brownian motion (GBM) with drift: dSt = rdt + σdWt , St where r is the continuously compounded risk-free rate, σ is the volatility parameter, Wt is the standard Brownian motion. This stochastic differential equation can be solved to show that the future log price is distributed as normal √ 1 log ST ∼ N log St + r − σ 2 τ, σ τ , 2 where τ = T − t > 0 is the time interval. This of course implies the log-normal risk-neutral conditional distribution qt (St+τ ; θ) for the price itself: 2 1 2 log (S /S ) − r − σ τ t T 1 1 2 √ √ qt (ST ; σ) = exp − . 2 σ τ ST 2πσ 2 Given the explicit form of the risk-neutral density we can easily price options using no-arbitrage 3 arguments by evaluating discounted risk-neutral expectation of the (call) option payoff, −rτ Ct (τ ; θ) = e h + Et (ST − K) i ˆ −rτ ∞ (ST − K) qt (ST ; σ) dST . =e K Here K is the strike of the contract, (x)+ = max (0, x), and (ST − K)+ is the payoff of the call option contract. The closed-form solution for the option price is a well-known Black-Scholes (BS) formula: Ct (τ ; θ) = St Φ (d1 ) − e−rτ KΦ (d2 ) , where log (St /K) + rτ 1 √ √ + σ τ, σ τ 2 d1 = √ d2 = d1 − σ τ , and Φ (·) is the cumulative standard normal probability function. Option price formula can be somewhat simplified if we normalize it by the current asset price and introduce log-forward moneyness x = log (K/St ) − rτ = log (K/Ft ): ct (x, τ, σ) = Ct (τ ; θ) /St = Φ (d1 ) − ex Φ (d2 ) , where 2.2 x 1 √ d1 = − √ + σ τ , σ τ 2 √ d2 = d1 − σ τ , Mixture of log-normals Now suppose, following Bahra (1996), Melik & Thomas (1997), and Söderlind & Svensson (1997)1 , that the risk-neutral density is in fact a mixture of various densities, qt (ST ; θ) = M X αi qit (ST ; µi , σi ) , M X αi = 1, αi ≥ 0, i=1 i=1 where M is the number of such densities with their own parameter vectors θi . Note that each of qi (ST ; θi ) is not yet required to be a risk-neutral one. Only the mixture has to possess this property. It easy to show that the option price is now simply a mixture of option prices each one corresponding to a single density qi (ST ; θi ): Ct (τ, r; θ) = M X ˆ −rτ ∞ (ST − K) qit (ST ; µi , σi ) dST = αi e K i=1 M X αi Cit (τ, r; µi , σi ) . i=1 If we keep the assumption of lognormality of each density in the mixture with parameters θi = (µi , σi ), then the option price is just a mixture of Black-Scholes prices with a new parameter µi instead of the risk-free rate r: Cit (τ, r; µi , σi ) = St Φ (di1 ) − e−rτ KΦ (di2 ) , 1 see also Jondeau et al. (2007, Ch. 11.3) for a on overview of the topic. 4 where di1 = √ di2 = di1 − σi τ . log (St /K) + µi τ 1 √ √ + σi τ , σi τ 2 BS formula is a specific case with α1 = 1 and µ1 = r. The normalized version is cit (x, τ, r; µi , σi ) = Φ (di1 ) − ex+(r−µi )τ Φ (di2 ) , where di1 = − x + (r − µi ) τ 1 √ √ + σi τ , σi τ 2 √ di2 = di1 − σi τ . The no-arbitrage condition boils down to the following assumption for the underlying stock price, St = e−rτ Et [ST ] , which after all substitutions can be reduced to exp (rτ ) = X αi exp (µi τ ) . i 2.3 Generalized Beta distribution Bookstaber & Mcdonald (1987) originally proposed to use generalized beta distribution of the second kind (GB2) to characterize stock returns. More recently, Liu et al. (2007) applied this distribution in the context of risk-neutral pricing. The advantage of this density is that it has enough flexibility to model four first moments separately, including skewness and kurtosis. The GB2 probability density function itself is written as q (x; [a, b, p, q]) = axap−1 , bap B (p, q) [1 + (x/b)a ]p+q X > 0, where B (p, q) = Γ (p) Γ (q) /Γ (p + q). Liu et al. (2007) assumed that the stock price itself, ST , is distributed according to GB2 distribution. Here we argue that a much more realistic assumption is that rather total excess return is distributed as GB2. Denote this random variable as R̃t,τ = ST −rτ e , St and assume that its density is q (x; θ) written above with a replaced by horizon dependent parameter aτ −1/2 . The moments of order n < qaτ −1/2 are given by h n Et R̃t,τ i √ √ bn B p + na τ , q − na τ = . B (p, q) 5 Hence, the martingale restriction is given by √ bB p + i h 1 = Et R̃t,τ = τ a ,q √ − τ a B (p, q) , ⇒ B (p, q) b= √ B p+ τ a ,q − √ τ a . The corresponding option price is given by ˆ Ct (τ, r; θ) =e −rτ ∞ (ST − K) qt (ST ; θ) dST K 1 1 =St 1 − G K; a, b, p + , q − a a (2.1) − Ke−rτ [1 − G (K; a, b, p, q)] , where G is the cdf of the GB2 distribution. For the proof see Section C in the Appendix. In empirical implementation this function can be computed through the cdf of beta distribution using the following relation: G (x; a, b, p, q) = Gβ (z (x; a, b) ; p, q) , h z (x; a, b) = 1 + (x/b)−a i−1 . So the price is actually Ct (τ, r; θ) = St 1 − Gβ 3 1 1 z (K; a, b) ; p + , q − a a − Ke−rτ [1 − Gβ (z (K; a, b) ; p, q)] . Option pricing Now suppose that we observe a large panel of option prices, {Ct (τ, x)}, which are indexed by time of observation t, maturity τ , and log-forward moneyness2 x = log (K/F ) = log (K/S) − rτ . On each date t we can find a parametric density which best describes the set observable options. Note that we already have a few closed-form option pricing formulas for each proposed risk-neutral density. Hence, we can minimize the sum of squared option pricing errors to find the optimal parameters for this specific day t. More specifically, the criterion function is θ̂t = arg min θ X [Ct (τ, x) − Ct (τ, x, rt ; θ)]2 . (3.1) x,τ In case of mixture of log-normals, the option price is given by Ct (τ, x, r; θ) = M X αk St [Φ (di1 ) − exj Φ (di2 )] , i=1 with di1 = 2 −x + (µi − r) τ 1 √ √ + σi τ , σi τ 2 √ di2 = di1 − σi τ , Renault & Touzi (1996) argue for the use of log-forward moneyness for its interesting theoretical properties 6 and the vector of parameters is θ = (αi , µi , σi )M i=1 . The no-arbitrage condition can be satisfied by adding the penalty to the objective function: #2 " penalty = X exp (rt τ ) − X τ . αi exp (µi τ ) i After performing the optimization problem in (3.1) we obtain a time series of parametric n densities qt St+τ ; θ̂t oT t=1 . The key question of this paper is whether there is any predictability in this object. Predictability in the space of parametric distributions is equivalent, on one hand, to predictability in ndynamics of parameters θ̂t , and on the other hand, to predictability in dynamics oT . Actually, option prices are more frequently quoted in terms of option prices Ct τ, x, r; θ̂t t=1 of BS implied volatilities which allow us to compare prices across different maturities, strikes, and current underlying price. The implied volatility σtimp (τ, x) is defined as the solution to the following equation: BS τ, x, r, σtimp (τ, x; θ) = Ct (τ, x, r; θ) , where BS (·) is the standard Black-Scholes formula. If, in addition, we convert option prices into the space of BS implied volatilities, then any predictable dynamics is also equivalent to predictability in the space of volatility surface σtimp (τ, x). n oT Next, given the time series of distribution parameters θ̂t t=1 , we can fit any time series model to the vector of parameters. Given the parameters of the time series model we construct the conditional one week forecast of the risk-neutral parameters. This gives us the second series of parameters n o n o θ̂tf T t=1 . This series is used to construct the forecast of risk-neutral densities, qt St+τ ; θ̂tf option prices, n Ct τ, x, r; θ̂tf oT t=1 , and implied volatility surfaces, n σtimp τ, x; θ̂tf oT t=1 T t=1 , . The last two objects can be compared to their realized counterparts using the well known measures, RM SE IV RM SE v u i2 u1 Xh = t , Ct (τ, x) − Ct τ, x, r; θ̂tf N t,x,τ v u i2 u 1 X h imp = t σt (τ, x) − σtimp τ, x; θ̂tf , N t,x,τ where N is the total number of terms in the summation P t,x,τ . The last one was put forward by Renault (1997) as a scale invariant measure of option pricing performance. 4 Results In this paper we use the volatility surface data from OptionMetrics. Similar to Heston & Nandi (2000); Christoffersen et al. (2008); Feunou & Tedongap (2012) we leave only Wednesday data to avoid any seasonality effects on the weekly frequency. Option premium is computed as a bid-ask average. Only options with positive bid and asks as well as bid-ask spread were left in the sample. 7 Finally, we limit our sample to options with maturities up to one year. After all the filters we have 87568 option quotes on the time interval from 10 January 1996 to 25 July 2012. Some descriptive statistics (together with results) is given in Table 2 on page 13, Table 3 on page 13, and Table 4 on page 14. There we sort options into bins by log-forward moneyness, maturity, and current VIX level. Given the data we solve optimization problem set in (3.1). To illustrate the point of the paper without chasing superior quantitative results we choose the simplest time series model possible to forecast parameters of the option-implied risk-neutral distributions. Specifically, we have chosen AR(3) for each parameter series separately. All the time series models are fit on the first half of the sample. Given the set of parameters of all AR(3) models we construct one week ahead forecast, θ̂tf . The result of this procedure is given in Figure 3 on page 25. Each panel shows time series plots of implied risk-neutral parameters θ̂t and their one week forecasts θ̂tf . The very top panel corresponds to the single parameter Black-Scholes model. The rest of the panels correspond to the mixture of two lognormals with total of five parameters, θ = (α, µ1 , µ2 , σ1 , σ2 ). The first panel, by construction, is closely related to BS implied volatility. It is different in the sense that it is calibrated to the whole volatility surface and not only to at-the-money one month options. Naturally, due to strong persistence in volatility this series is highly predictable. ACF and PACF plots for all parameters can be found in Figure 4 on page 25. On the same figure we notice that parameters of log-normal mixture model also demonstrate some degree of predictability. Coming back to Figure 3 on page 25 we see that on average parameter α is close to 0.9. This means that the log-normal density with parameters µ1 and σ1 plays the main role in describing risk-neutral densities. To illustrate the result we draw a single day density on Figure 7 on page 28. This picture shows two risk-neutral densities of the log return, log (St+τ /St ), with τ = 1. The first density corresponds to the simple Black-Scholes model. Clearly, it is just a normal density centered at the risk-free rate. The second density is a mixture of two normals. We can see that it is a bi-modal density with fat tails by construction. On the same day we compute option prices and corresponding implied volatilities and plot them along with observables on Figure 8 on page 29. Each panel corresponds to a different maturity available on this date. In the real data we can clearly see the well known phenomena called volatility smirk. We can also immediately notice a trivial result that the Black & Scholes (1973) implied volatilities are flat across moneyness. Finally, the crucial result shown in this figure is that the log-normal mixture is able to reproduce the volatility smile at least qualitatively on all horizons. Next, we analyze the results of out-of-sample option pricing on the whole sample. First of all we need to look at Table 2 on page 13 which shows aggregated statistics across several moneyness bins. There we can see that the IVRMSE for the BS and mixture model is 3.42% and 3.29%, respectively. We need to stress that this result is out-of-sample. Analyzing IVRMSE on a more detailed scale we can see that the mixture model outperforms the simplest BS model especially for out-of-the-money options. When we sort options into bins according to maturity, Table 3 on page 13, we can see that the mixture is almost universally better than its specific case. Finally, after sorting options by the 8 current VIX level, Table 4 on page 14, there is also no clear pattern of over performance. Going even further and performing a double sort by moneyness and maturity we can get even closer perspective on the results by looking at Figure 10 on page 32. There we see that the BS model produces universally flat volatility surfaces, while the mixture model matches the observable option prices much closer. Next, looking at the pricing error in Figure 11 on page 33 we see that BS model error is mostly concentrated in out-of-the-money side while the mixture model error is more uniform but minimal at-the-money. Squaring the errors and then taking the average across several bins gives us Figure 13 on page 35. Looking from the time perspective on Figure 15 on page 37 (bottom panel) we can see that the option pricing error is not correlated, at least visually, with the current volatility as measured by the VIX index. Moreover, there are no noticeable time series patterns in the relation between two model errors. To conclude this section we compare our option pricing performance represented by total IVRMSE to other results in the literature. Feunou & Tedongap (2012) for comparison purposes, besides their own model with conditional skewness, also estimate discrete-time model by Heston & Nandi (2000), Christoffersen et al. (2006), Christoffersen et al. (2008), as well as continuous-time model used by Pan (2002), Andersen et al. (2002), Chernov et al. (2003), and Bates (2006). Feunou & Tedongap (2012) show that among these models the best IVRMSE is in vicinity of 2.5%. Corsi et al. (2013) in their model which targets long memory in volatility process produce 3.8%. Majewski et al. (2013) do even better but not uniformly across all option subsets. Christoffersen et al. (2009) reach 2% in-sample with the multi-factor volatility model. Hence, our option pricing model although very simple has a potential to compete with the stat-of-the-art option pricing models. 5 Conclusion In this paper we propose a novel approach to option pricing. It builds on the well established empirical fact that option-implied information is highly predictable. Our simple illustrative model nevertheless produces quite good option pricing performance as measured by IVRMSE across moneyness, maturity, and time. At the same time we see several avenues for further improvement. First of all, we only use a mixture of two log-normal distributions and Generalized Beta distribution. Although they produce some asymmetry and fatter tails in comparison to a single log-normal, they are far away from flexibility of other parametric distributions. Besides, the mixture has some computational and identification issues. To remedy that we plan to try other parametric distributions mentioned in Jondeau et al. (2007) and Christoffersen et al. (2012a). 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Appendix A A.1 Tables Summary Table 1: Summary of option pricing sample model Price error IV error RMSE IVRMSE in BS GB2 MBS -0.02 0.46 -0.53 -0.12 0.31 -0.47 4.53 2.28 2.57 2.65 1.72 1.98 out BS GB2 MBS 0.08 -0.30 -0.28 -0.06 -0.06 -0.33 5.45 4.48 4.12 2.94 2.59 2.30 12 A.2 A.2.1 One level sort Premium Table 2: Option premiums by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count mean std 14999 29.23 17.31 9012 35.02 22.32 20895 34.25 20.02 10797 27.01 19.23 18509 24.46 16.60 mean std mean std mean std 23.35 15.84 29.30 16.43 28.06 18.43 32.14 20.87 35.58 21.04 34.21 23.36 34.61 19.05 35.27 19.10 33.27 19.91 29.46 18.75 27.59 18.66 26.59 18.33 28.72 16.94 24.46 16.19 25.02 15.89 mean std mean std mean std 23.39 15.66 28.43 15.14 28.22 18.10 32.22 20.60 34.74 19.53 34.44 22.88 34.85 18.89 34.88 18.01 33.71 19.61 29.60 18.49 26.97 17.34 26.88 17.98 28.70 16.73 23.34 14.75 25.11 15.53 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS Table 3: Option premiums by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count mean std 10892 13.43 7.53 10691 19.20 10.34 29527 27.97 14.50 8885 36.02 16.97 14217 50.40 21.54 mean std mean std mean std 13.64 6.39 14.83 7.06 12.73 5.72 19.36 9.11 20.54 9.89 18.25 8.35 28.10 13.37 28.79 14.21 26.95 12.97 35.90 16.12 36.10 17.00 35.13 16.13 49.83 21.40 48.93 21.74 51.55 22.83 mean std mean std mean std 13.66 6.34 14.31 6.46 12.82 5.54 19.39 8.99 19.89 9.02 18.38 8.05 28.19 13.16 28.03 12.98 27.18 12.52 36.03 15.75 35.25 15.36 35.45 15.48 50.07 20.86 48.00 19.58 52.01 21.95 BS in GB2 MBS BS out GB2 MBS 13 Table 4: Option premiums by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count mean std 14957 19.08 11.29 20920 25.75 15.19 22060 31.73 17.83 8705 36.89 19.60 7570 48.72 26.57 mean std mean std mean std 19.48 10.38 19.65 10.20 19.14 11.17 26.20 14.25 26.42 14.02 25.68 15.17 31.94 17.01 32.33 16.80 31.36 17.95 36.50 19.34 37.18 19.21 35.89 20.14 46.37 27.26 48.12 27.55 45.80 27.96 mean std mean std mean std 20.36 10.70 20.71 10.54 20.51 11.64 26.78 14.62 26.88 14.30 26.66 15.68 32.05 17.24 31.75 16.74 31.49 18.16 35.90 19.39 34.88 18.62 35.10 20.08 44.40 26.87 41.65 24.79 43.40 26.98 BS in GB2 MBS BS out GB2 MBS A.2.2 Implied volatility Table 5: Option implied volatilities by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count mean std 14999 23.25 6.45 9012 21.05 6.35 20895 18.30 5.85 10797 17.79 5.71 18509 18.86 5.63 mean std mean std mean std 20.04 5.17 23.38 6.30 22.18 5.42 19.54 5.33 21.51 5.95 20.24 5.52 18.52 5.02 18.96 5.49 17.62 4.96 19.12 5.09 18.17 5.37 17.62 4.82 20.70 5.29 18.81 5.18 19.12 5.09 mean std mean std mean std 20.07 5.03 22.92 5.43 22.26 5.14 19.61 5.18 21.15 5.10 20.39 5.19 18.65 4.89 18.77 4.78 17.86 4.70 19.20 4.94 17.88 4.61 17.79 4.58 20.69 5.15 18.27 4.37 19.16 4.85 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS 14 Table 6: Option implied volatilities by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count mean std 10892 20.13 7.79 10691 20.01 6.89 29527 19.65 6.02 8885 19.49 5.61 14217 19.38 5.41 mean std mean std mean std 20.20 5.50 21.42 6.80 19.41 5.77 20.00 5.30 20.88 6.27 19.33 5.48 19.60 5.12 19.98 5.72 19.09 5.22 19.28 5.10 19.39 5.51 19.02 5.25 18.96 5.19 18.74 5.39 19.44 5.59 mean std mean std mean std 20.22 5.35 20.89 5.91 19.52 5.46 20.03 5.15 20.42 5.47 19.44 5.19 19.65 4.98 19.63 5.00 19.23 4.96 19.36 4.96 19.08 4.79 19.18 5.00 19.05 5.05 18.49 4.70 19.61 5.36 BS in GB2 MBS BS out GB2 MBS Table 7: Option implied volatilities by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count mean std 14957 12.79 1.99 20920 17.14 2.68 22060 21.00 2.72 8705 24.38 2.94 7570 31.27 7.25 mean std mean std mean std 13.09 1.07 13.28 1.81 12.81 1.74 17.39 2.03 17.67 2.76 17.03 2.44 21.07 1.80 21.47 2.90 20.69 2.37 23.94 1.63 24.53 3.14 23.59 2.36 29.16 5.06 30.32 6.58 28.76 5.38 mean std mean std mean std 13.48 1.13 13.76 1.83 13.44 1.78 17.65 2.27 17.88 2.91 17.48 2.67 21.11 2.15 21.19 3.03 20.74 2.65 23.65 2.19 23.42 3.30 23.21 2.75 28.38 5.55 27.27 6.07 27.92 5.53 BS in GB2 MBS BS out GB2 MBS 15 A.2.3 Premium bias Table 8: Option premium error by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count 14999 9012 20895 10797 18509 mean std mean std mean std -5.89 3.08 0.07 2.14 -1.18 2.88 -2.89 2.82 0.56 2.41 -0.82 3.00 0.37 2.54 1.02 2.29 -0.98 2.31 2.45 2.25 0.59 2.15 -0.42 2.12 4.26 2.55 0.00 2.03 0.56 1.95 mean std mean std mean std -5.84 4.31 -0.80 4.44 -1.01 4.43 -2.81 4.31 -0.28 4.98 -0.58 4.69 0.60 3.79 0.64 4.17 -0.54 3.86 2.59 3.71 -0.04 4.18 -0.13 3.77 4.24 4.10 -1.13 4.51 0.65 3.80 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS Table 9: Option premium error by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count 10892 10691 29527 8885 14217 mean std mean std mean std 0.21 3.58 1.40 2.60 -0.70 2.85 0.16 4.02 1.34 2.32 -0.95 2.83 0.13 4.36 0.83 1.53 -1.02 2.21 -0.12 4.64 0.08 0.93 -0.89 1.39 -0.57 5.64 -1.47 2.45 1.15 2.42 mean std mean std mean std 0.23 4.17 0.88 3.95 -0.61 3.68 0.19 4.81 0.69 4.27 -0.82 4.02 0.22 5.34 0.06 4.26 -0.79 3.98 0.02 5.71 -0.77 4.19 -0.56 3.78 -0.34 6.66 -2.41 4.83 1.61 4.38 BS in GB2 MBS BS out GB2 MBS 16 Table 10: Option premium error by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count 14957 20920 22060 8705 7570 mean std mean std mean std 0.40 3.39 0.56 1.75 0.06 1.05 0.44 3.99 0.67 2.20 -0.08 1.42 0.21 4.35 0.60 2.09 -0.36 1.91 -0.39 4.81 0.29 1.83 -1.00 2.60 -2.35 6.78 -0.59 3.38 -2.92 5.34 mean std mean std mean std 1.28 3.55 1.63 1.93 1.43 1.75 1.03 4.53 1.13 2.93 0.90 2.75 0.32 4.97 0.03 3.26 -0.24 3.08 -1.00 5.67 -2.02 3.77 -1.79 3.94 -4.32 8.60 -7.07 7.41 -5.31 7.43 BS in GB2 MBS BS out GB2 MBS A.2.4 Implied volatility bias Table 11: Option implied volatility error by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count 14999 9012 20895 10797 18509 mean std mean std mean std -3.21 2.19 0.12 1.68 -1.08 2.21 -1.51 1.92 0.46 1.89 -0.81 2.09 0.22 1.84 0.66 1.72 -0.68 1.67 1.33 1.74 0.38 1.53 -0.16 1.66 1.84 1.74 -0.05 1.58 0.25 1.72 mean std mean std mean std -3.19 2.59 -0.33 2.60 -0.99 2.55 -1.44 2.31 0.10 2.80 -0.66 2.41 0.35 2.23 0.48 2.48 -0.44 2.15 1.41 2.20 0.09 2.37 0.00 2.14 1.82 2.08 -0.60 2.60 0.30 1.98 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS 17 Table 12: Option implied volatility error by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count 10892 10691 29527 8885 14217 mean std mean std mean std 0.07 3.87 1.29 2.87 -0.72 3.26 -0.01 3.07 0.87 1.88 -0.68 2.33 -0.05 2.41 0.33 1.15 -0.56 1.53 -0.21 2.05 -0.10 0.81 -0.47 1.08 -0.42 1.81 -0.64 0.93 0.06 1.03 mean std mean std mean std 0.09 4.24 0.76 4.08 -0.61 3.62 0.02 3.42 0.41 3.03 -0.57 2.76 0.00 2.70 -0.02 2.18 -0.42 1.96 -0.13 2.29 -0.41 1.72 -0.31 1.46 -0.33 1.98 -0.89 1.51 0.24 1.23 BS in GB2 MBS BS out GB2 MBS Table 13: Option implied volatility error by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count 14957 20920 22060 8705 7570 mean std mean std mean std 0.29 1.67 0.49 1.01 0.02 0.62 0.25 2.07 0.53 1.33 -0.11 0.85 0.07 2.30 0.47 1.30 -0.31 1.12 -0.44 2.64 0.15 1.21 -0.79 1.56 -2.12 4.82 -0.95 3.56 -2.51 4.66 mean std mean std mean std 0.69 1.76 0.97 1.17 0.64 0.87 0.52 2.31 0.74 1.66 0.34 1.35 0.11 2.55 0.20 1.71 -0.25 1.60 -0.73 2.97 -0.96 1.84 -1.17 2.09 -2.90 4.92 -4.00 4.75 -3.36 4.31 BS in GB2 MBS BS out GB2 MBS 18 A.2.5 RMSE Table 14: RMSE by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count 14999 9012 20895 10797 18509 mean std mean std mean std 44.15 52.83 4.57 11.31 9.66 32.43 16.26 38.81 6.10 12.66 9.66 33.10 6.59 20.62 6.29 12.76 6.29 28.81 11.04 19.18 4.95 12.76 4.67 22.32 24.66 28.43 4.10 14.07 4.12 15.55 mean std mean std mean std 52.69 91.18 20.34 74.43 20.67 64.37 26.47 78.69 24.88 87.61 22.37 72.37 14.71 43.90 17.78 62.97 15.19 55.03 20.51 45.08 17.51 64.67 14.25 52.81 34.77 57.76 21.61 81.41 14.85 47.31 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS Table 15: RMSE by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count 10892 10691 29527 8885 14217 mean std mean std mean std 12.87 41.01 8.69 19.90 8.60 38.09 16.17 39.00 7.19 13.55 8.92 33.67 19.02 29.92 3.03 6.30 5.92 18.89 21.51 25.51 0.87 2.57 2.74 6.49 32.11 43.99 8.14 17.06 7.17 31.54 mean std mean std mean std 17.47 57.55 16.38 59.08 13.89 57.52 23.13 64.37 18.72 70.52 16.85 64.75 28.53 61.57 18.17 72.48 16.48 57.70 32.60 59.56 18.14 70.69 14.62 46.03 44.42 79.33 29.11 88.45 21.79 57.12 BS in GB2 MBS BS out GB2 MBS 19 Table 16: RMSE by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count 14957 20920 22060 8705 7570 mean std mean std mean std 11.63 15.08 3.38 4.13 1.10 2.18 16.10 23.36 5.30 9.01 2.03 2.68 18.97 25.32 4.72 8.29 3.78 5.34 23.31 26.91 3.43 5.64 7.77 9.88 51.52 83.59 11.77 32.69 36.99 75.77 mean std mean std mean std 14.27 16.18 6.38 6.89 5.10 8.52 21.60 38.51 9.87 21.58 8.38 29.73 24.76 37.99 10.66 21.40 9.57 17.46 33.15 48.75 18.29 34.21 18.72 29.12 92.64 160.73 104.85 202.78 83.49 151.09 BS in GB2 MBS BS out GB2 MBS A.2.6 IVRMSE Table 17: IVRMSE by moneyness sample (−2, +2] (+2, +4] (+2, +∞) count 14999 9012 20895 10797 18509 mean std mean std mean std 15.08 57.32 2.83 49.81 6.04 67.75 5.98 51.03 3.77 48.06 5.01 63.26 3.44 35.13 3.39 33.85 3.26 42.36 4.82 24.84 2.48 23.82 2.78 31.72 6.41 37.83 2.49 38.68 3.03 43.13 mean std mean std mean std 16.89 43.95 6.88 54.54 7.48 33.93 7.40 30.82 7.86 52.81 6.25 29.47 5.08 19.92 6.36 38.18 4.80 22.82 6.82 16.12 5.62 30.30 4.57 18.63 7.65 16.77 7.11 50.04 4.00 17.39 data GB2 MBS BS out (−4, −2] stat BS in (−∞, −4] model GB2 MBS 20 Table 18: IVRMSE by maturity sample model stat (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) data count 10892 10691 29527 8885 14217 mean std mean std mean std 14.95 78.60 9.88 71.47 11.14 95.82 9.44 48.32 4.28 45.20 5.89 56.76 5.82 31.80 1.43 30.86 2.65 36.50 4.23 23.56 0.67 23.18 1.39 27.44 3.45 18.61 1.29 18.24 1.07 21.37 mean std mean std mean std 17.98 56.79 17.26 86.82 13.46 52.21 11.73 30.49 9.35 52.01 7.93 28.22 7.31 15.56 4.73 33.51 4.02 13.61 5.27 9.43 3.11 24.55 2.22 6.68 4.04 6.92 3.08 19.23 1.57 4.18 BS in GB2 MBS BS out GB2 MBS Table 19: IVRMSE by current VIX level sample model stat (0, 15] (15, 20] (20, 25] (25, 30] (30, +∞) data count 14957 20920 22060 8705 7570 mean std mean std mean std 2.87 3.17 1.25 2.04 0.39 0.83 4.34 5.82 2.07 4.36 0.73 1.39 5.27 7.09 1.92 4.60 1.36 2.38 7.16 10.37 1.50 3.19 3.06 5.13 27.74 129.21 13.57 122.63 28.04 155.25 mean std mean std mean std 3.56 3.98 2.31 3.38 1.17 1.92 5.58 8.44 3.31 6.45 1.95 4.36 6.49 9.40 2.97 5.85 2.61 4.47 9.34 14.14 4.29 6.72 5.75 8.77 32.59 76.89 38.64 138.74 29.88 71.47 BS in GB2 MBS BS out GB2 MBS 21 A.3 Two-level sort Table 20: Ratios of RMSE by moneyness and maturity Moneyness sample model Maturity (−∞, −4] (−4, −2] (−2, +2] (+2, +4] (+2, +∞) GB2 (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.24 0.17 0.05 0.01 0.15 0.79 0.55 0.24 0.04 0.39 1.02 1.00 0.80 0.52 1.15 0.54 0.45 0.30 0.16 0.85 0.93 0.39 0.12 0.03 0.19 MBS (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.59 0.45 0.21 0.05 0.16 0.83 0.79 0.48 0.12 0.70 0.73 0.85 1.16 1.35 1.18 0.49 0.40 0.49 0.52 0.14 0.82 0.46 0.19 0.09 0.06 GB2 (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.47 0.43 0.36 0.32 0.42 1.01 0.95 0.92 0.88 0.96 1.14 1.17 1.19 1.23 1.37 0.77 0.76 0.79 0.81 1.19 1.69 0.98 0.58 0.48 0.58 MBS (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.68 0.58 0.40 0.25 0.33 0.94 0.96 0.81 0.58 0.91 0.86 0.95 1.09 1.13 1.19 0.65 0.63 0.72 0.74 0.71 0.91 0.66 0.45 0.38 0.34 in out 22 Table 21: Ratios of IVRMSE by moneyness and maturity Moneyness sample model Maturity (−∞, −4] (−4, −2] (−2, +2] (+2, +4] (+2, +∞) GB2 (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.29 0.20 0.11 0.08 0.22 0.86 0.65 0.46 0.35 0.41 1.02 1.00 0.84 0.72 1.12 0.53 0.51 0.39 0.20 1.17 1.04 0.47 0.22 0.14 0.34 MBS (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.65 0.47 0.31 0.17 0.18 0.93 0.96 0.85 0.64 0.30 0.81 0.98 1.20 1.53 1.25 0.52 0.50 0.71 1.37 0.70 1.02 0.62 0.34 0.25 0.25 GB2 (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.46 0.41 0.36 0.34 0.45 1.10 1.07 1.06 1.04 0.94 1.19 1.23 1.30 1.43 1.82 0.74 0.79 0.84 0.91 1.90 2.34 1.07 0.63 0.55 0.76 MBS (0, 30] (30, 90] (90, 180] (180, 270] (270, +∞) 0.62 0.53 0.38 0.23 0.22 0.93 0.95 0.82 0.57 0.59 0.85 0.96 1.12 1.17 0.94 0.64 0.62 0.73 0.85 0.79 0.87 0.63 0.45 0.38 0.37 in out B Figures B.1 Distribution parameters Figure 1: Calibrated model parameters and out-of-sample forecasts for BS model 0 .5 0 0 .4 5 0 .4 0 0 .3 5 0 .3 0 0 .2 5 0 .2 0 0 .1 5 0 .1 0 s ig m a IN OUT 19 97 19 99 20 01 20 05 20 da te 03 23 20 07 20 09 20 11 Figure 2: Calibrated model parameters and out-of-sample forecasts for MBS model 0 .7 5 0 .7 0 0 .6 5 0 .6 0 0 .5 5 0 .5 0 0 .4 5 0 .4 0 0 .0 5 0 .0 0 − 0 .0 5 − 0 .1 0 − 0 .1 5 − 0 .2 0 0 .2 0 a IN OUT m1 IN OUT m2 0 .1 5 IN OUT 0 .1 0 0 .0 5 0 .0 0 0 .7 0 .6 0 .5 0 .4 0 .3 0 .2 0 .1 0 .0 0 .2 5 0 .2 0 0 .1 5 0 .1 0 0 .0 5 0 .0 0 s1 IN OUT s2 IN OUT 19 97 19 99 20 01 20 05 20 da te 03 24 20 07 20 09 20 11 Figure 3: Calibrated model parameters and out-of-sample forecasts for GB2 model 8 7 6 5 4 3 2 1 0 .0 2 5 0 .0 2 0 0 .0 1 5 0 .0 1 0 0 .0 0 5 0 .0 0 0 a IN OUT p IN OUT 19 97 19 99 20 01 20 05 20 da te 03 20 07 20 09 20 11 Figure 4: Calibrated model parameters for BS model, ACF and PACF 1.0 0.8 0.6 0.4 0.2 0.0 0.2 0.4 ACF: sigma 0 5 10 15 lags, weeks PACF: sigma 1.0 0.8 0.6 0.4 0.2 0.0 20 25 25 0 5 10 15 lags, weeks 20 25 Figure 5: Calibrated model parameters for MBS model, ACF and PACF ACF: a 1.0 0.8 0.6 0.4 0.2 0.0 0.2 ACF: m1 1.0 0.8 0.6 0.4 0.2 0.0 0.2 1.0 0.8 0.6 0.4 0.2 0.0 0.2 5 10 15 lags, weeks PACF: s1 1.0 0.8 0.6 0.4 0.2 0.0 ACF: s2 0 PACF: m2 1.0 0.8 0.6 0.4 0.2 0.0 ACF: s1 1.0 0.8 0.6 0.4 0.2 0.0 0.2 PACF: m1 1.0 0.8 0.6 0.4 0.2 0.0 ACF: m2 1.0 0.8 0.6 0.4 0.2 0.0 0.2 PACF: a 1.0 0.8 0.6 0.4 0.2 0.0 PACF: s2 1.0 0.8 0.6 0.4 0.2 0.0 20 25 0 26 5 10 15 lags, weeks 20 25 Figure 6: Calibrated model parameters for GB2 model, ACF and PACF 1.0 0.8 0.6 0.4 0.2 0.0 0.2 0.4 1.0 0.8 0.6 0.4 0.2 0.0 0.2 ACF: a ACF: p 0 5 10 15 lags, weeks PACF: a 1.0 0.8 0.6 0.4 0.2 0.0 20 25 27 1.0 0.8 0.6 0.4 0.2 0.0 PACF: p 0 5 10 15 lags, weeks 20 25 B.2 One day example Figure 7: Implied risk-neutral densities of the returns for one day 5 4 3 2 1 0 − 1 .0 − 0 .5 0 .0 Lo g re t u rn 28 0 .5 1 .0 Figure 8: Implied volatility for one day 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 19 18 17 16 15 14 13 12 Da ys , 3 0 Da ys , 6 0 Da ys , 9 1 Da ys , 1 2 2 Da ys , 1 5 2 Da ys , 1 8 2 Da ys , 2 7 3 Da ys , 3 6 5 BS GB2 MBS im p _vo l_d a t a −5 0 Mo n e yn e s s , % 29 5 30 B.3 Option pricing results B.3.1 Absolute values p re m iu m p re m iu m 70 60 50 40 30 20 10 0 p re m iu m 70 60 50 40 30 20 10 0 70 60 50 40 30 20 10 0 p re m iu m 70 60 50 40 30 20 10 0 p re m iu m Figure 9: Premiums, two level sort Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] 70 60 In s a m p le 50 BS 40 GB2 30 MBS 20 p re m iu m _d a t a 10 0 (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % 31 Ou t o f s a m p le BS GB2 MBS p re m iu m _d a t a (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] Mo n e yn e s s , % (4 , 1 0 ] im p _vo l im p _vo l 30 28 26 24 22 20 18 16 im p _vo l 30 28 26 24 22 20 18 16 30 28 26 24 22 20 18 16 im p _vo l 30 28 26 24 22 20 18 16 im p _vo l Figure 10: Implied volatilities, two level sort Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] 30 28 In s a m p le 26 BS 24 GB2 22 MBS 20 im p _vo l_d a t a 18 16 (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % 32 Ou t o f s a m p le BS GB2 MBS im p _vo l_d a t a (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] Mo n e yn e s s , % (4 , 1 0 ] B.3.2 Relative errors Figure 11: Premium error, two level sort Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] p e rro r 4 2 0 −2 −4 p e rro r 4 2 0 −2 −4 p e rro r 4 2 0 −2 −4 p e rro r 4 2 0 −2 −4 p e rro r 4 2 0 In s a m p le Ou t o f s a m p le BS GB2 MBS BS GB2 MBS −2 −4 ( 1 0 , 4 ] ( 4 , 2 ] ( 2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % 33 ( 1 0 , 4 ] ( 4 , 2 ] ( 2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % Figure 12: Implied volatility error, two level sort Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] ve rro r 4 2 0 −2 −4 ve rro r 4 2 0 −2 −4 ve rro r 4 2 0 −2 −4 ve rro r 4 2 0 −2 −4 ve rro r 4 2 0 In s a m p le Ou t o f s a m p le BS GB2 MBS BS GB2 MBS −2 −4 ( 1 0 , 4 ] ( 4 , 2 ] ( 2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % 34 ( 1 0 , 4 ] ( 4 , 2 ] ( 2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % B.3.3 Absolute errors Figure 13: RMSE, two level sort 10 Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] p e rro r2 8 6 4 2 0 10 p e rro r2 8 6 4 2 0 10 p e rro r2 8 6 4 2 0 10 p e rro r2 8 6 4 2 0 10 p e rro r2 8 6 4 In s a m p le Ou t o f s a m p le BS GB2 MBS BS GB2 MBS 2 0 (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] Mo n e yn e s s , % (4 , 1 0 ] 35 (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] Mo n e yn e s s , % (4 , 1 0 ] ve rro r2 8 7 6 5 4 3 2 1 0 ve rro r2 8 7 6 5 4 3 2 1 0 ve rro r2 8 7 6 5 4 3 2 1 0 ve rro r2 Figure 14: IVRMSE, two level sort 8 7 6 5 4 3 2 1 0 Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (0 , 3 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (3 0 , 9 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (9 0 , 1 8 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (1 8 0 , 2 7 0 ] Ma t u rit y, (2 7 0 , 3 6 6 ] Ma t u rit y, (2 7 0 , 3 6 6 ] ve rro r2 8 7 In s a m p le 6 BS 5 GB2 4 MBS 3 2 1 0 (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] (4 , 1 0 ] Mo n e yn e s s , % 36 Ou t o f s a m p le BS GB2 MBS (-1 0 , -4 ] (-4 , -2 ] (-2 , 2 ] (2 , 4 ] Mo n e yn e s s , % (4 , 1 0 ] B.3.4 Errors across time Figure 15: Implied volatility over time VIX VIX da te da te Im p vo l Im p vo l 80 70 60 50 40 30 20 10 0 80 70 60 50 m ode l m ode l BS GB2 MBS im p _vo l_d a t a BS GB2 MBS im p _vo l_d a t a 40 30 20 10 0 80 70 60 50 da te da te IVRMSE IVRMSE m ode l m ode l BS GB2 MBS BS GB2 MBS 40 30 20 10 0 19 97 999 001 003 005 007 009 011 1 2 2 2 2 2 2 da te 19 37 97 999 001 003 005 007 009 011 1 2 2 2 2 2 2 da te C C.1 Proofs Proof of (2.1) The option price is + ct (x, τ ; θ) =Et R̃t,τ − ex , ˆ ˆ ∞ = uqt (u; θ) du − ex ∞ qt (u; θ) du. ex ex Write the term under the first integral separately: uqt (u; [a, b, p, q]) = = = auap bap B (p, q) [1 + (u/b)a ]p+q aua(p+1/a)−1 ba(p+1/a) b−1 B (p, q) [1 + (u/b)a ](p+1/a)+(q−1/a) 1 aua(p+ a )−1 1 ba(p+ a ) B p + a1 , q − =qt 1 a 1 1 u; a, b, p + , q − a a 1 1 [1 + (u/b)a ](p+ a )+(q− a ) . The expression under the integral becomes a reparameterized density function, so ct (x, τ ; θ) =Et x R̃t,τ − e + , 1 1 = 1 − Gt ex ; a, b, p + , q − a a 38 − ex [1 − Gt (ex ; [a, b, p, q])] .
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