Time-Consistent and Market-Consistent Actuarial Valuations Antoon Pelsser1 Mitja Stadje2 1 Maastricht University & Kleynen Consultants & Netspar Email: [email protected] 2 Tilburg University & Netspar 23 May 2013 ASTIN Conference – Den Haag A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 1 / 34 Introduction Motivation Standard actuarial premium principles usually consider “static” premium calculation: What is price today of insurance contract with payoff at time T ? Actuarial premium principles typically “ignore” financial markets Financial pricing considers “dynamic” pricing problem: How does price evolve over time until time T ? Financial pricing typically “ignores” unhedgeable risks Examples: Pricing Pricing Pricing Pricing very long-dated cash flows T ∼ 30 − 100 years long-dated options T > 5 years pension & insurance liabilities employee stock-options A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 2 / 34 Introduction Ambitions In this joint paper with Mitja Stadje: [Pelsser and Stadje, 2013] we want to combine 1 2 Time-Consistent pricing operators, see [Jobert and Rogers, 2008] Market-Consistent pricing operators, see [Malamud et al., 2008] We will be interested in continuous-time limits of these discrete algorithms for different actuarial premium principles: 1 2 3 4 Variance Principle Mean Value Principle Standard-Deviation Principle Cost-of-Capital Principle A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 3 / 34 Introduction Content of This Talk 1 Pure Insurance Risk Diffusion Model for Insurance Risk Variance Principle (→ exponential indiff. pricing) Standard-Dev. Principle (→ E[] under new measure) Cost-of-Capital Principle (→ St.Dev price) Davis Price, see [Davis, 1997] St.Dev is “small perturbation” of Variance price 2 Financial & Insurance Risk Diffusion Model for Financial Risk Market-Consistent Pricing Variance Principle Numerical Illustration 3 Conclusions A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 4 / 34 Pure Insurance Risk Model for Insurance Risk Pure Insurance Model Consider unhedgeable insurance process y : dy = a(t, y ) dt + b(t, y ) dW To keep math simple, concentrate on diffusion setting Discretisation scheme as binomial tree: √ +b √∆t with prob. y (t + ∆t) = y (t) + a∆t + −b ∆t with prob. A. Pelsser (Maastricht U) TC & MC Valuations 1 2 1 2 23 May 2013 – ASTIN 5 / 34 Pure Insurance Risk Time Consistency Time Consistency Time Consistent price π(t, y ) satisfies property π[f (y (T ))|t, y ] = π[π[f (y (T ))|s, y (s)]|t, y ] ∀t < s < T Price of today of holding claim until T is the same as buying claim half-way at time s for price π(s, y (s)) “Semi-group property” Similar idea as “tower property” of conditional expectation A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 6 / 34 Pure Insurance Risk Variance Principle Variance Principle Actuarial Variance Principle Πv : Πvt [f (y (T ))] = Et [f (y (T ))] + 21 αVart [f (y (T ))] α is Absolute Risk Aversion Apply Πv to one binomial time-step to obtain price π v : π v t, y (t) = Et [π v t + ∆t, y (t + ∆t) ] + v 1 2 αVart [π t + ∆t, y (t + ∆t) ] Note: we omit discounting for now A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 7 / 34 Pure Insurance Risk Variance Principle Pricing PDE Assume π v (t, y ) admits Taylor approximation in y Evaluate Var.Princ. for binomial step & take limit for ∆t → 0 Same as derivation of Feynman-Kaç, but for E[] + 12 αVar[] This leads to pde for π v : v + 12 α(bπyv )2 = 0 πtv + aπyv + 21 b 2 πyy Note, non-linear term = “local unhedgeable variance” b 2 (πyv )2 Find general solution to this non-linear pde via log-transform: h i 1 v αf (y (T )) π (t, y ) = ln Et e y (t) = y . α Exponential indifference price, see [Henderson, 2002] or [Musiela and Zariphopoulou, 2004] A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 8 / 34 Pure Insurance Risk Variance Principle Include Discounting We should include discounting into our pricing Absolute Risk Aversion α is not “unit-free”, but has unit 1/e This conveniently compensates the unit (e)2 of Var[]. . . Therefore, “α-today” is different than “α-tomorrow” Relative Risk Aversion γ is unit-free Express ARA relative to “benchmark wealth” X0 e rT Explicit notation: α → γ/X0 e rT leads to pde: v πtv + aπyv + 12 b 2 πyy + v 2 1 γ 2 X e rt (bπy ) 0 − r πv = 0 γ f (y (T )) X0 e rt X0 e rT π (t, y ) = ln E e y (t) = y γ v Note: express all prices in discounted terms A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 9 / 34 Pure Insurance Risk Variance Principle Backward Stochastic Differential Equations Pricing PDE: v πtv + aπyv + 12 b 2 πyy + v 2 1 γ 2 X e rt (bπy ) 0 − r πv = 0 This non-linear PDE, represents the solution to a so-called BSDE for the triplet of processes (yt , Yt , Zt ) dyt = a(t, yt ) dt + b(t, yt ) dWt dYt = −g (t, yt , Yt , Zt ) dt + Zt dWt YT = f y (T ) , with “generator” g (t, y , Y , Z ) = 21 X0γe rt Z 2 − rY . Recent literature studies uniqueness & existence of solutions to BSDE’s, see [El Karoui et al., 1997] Via BSDE’s we can study time-consistent pricing operators in a much more general stochastic setting. But we will not pursue this here. A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 10 / 34 Pure Insurance Risk Mean Value Principle Mean Value Principle Generalise to Mean Value Principle −1 Πm (Et [v (f (y (T )))]) t [f (y (T ))] = v for any function v () which is a convex and increasing Exponential pricing is special case with v (x) = e αx Do Taylor-expansion & limit ∆t → 0: mf + πtmf + aπymf + 12 b 2 πyy 00 mf mf 2 1 v (π ) 2 v 0 (π mf ) (bπy ) =0 Note: π mf (t, y ) := π m (t, y )/e rt is price expressed in discounted terms Interpretation as generalised Variance Principle with “local risk aversion” term: v 00 ()/v 0 () A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 11 / 34 Pure Insurance Risk Standard-Deviation Principle Standard-Deviation Principle Actuarial Standard-Deviation Principle: Πst [f (y (T ))] = Et [f (y (T ))] + β p Vart [f (y (T ))]. Pay attention to “time-scales”: Expectation scales with √ ∆t St.Dev. scales with ∆t √ Thus, we should take β ∆t to get well-defined limit √ Note: β has unit 1/ time A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 12 / 34 Pure Insurance Risk Standard-Deviation Principle Pricing PDE Do Taylor-expansion & limit ∆t → 0: q s πts + aπys + 12 b 2 πyy + β (bπys )2 − r π s = 0 Again, non-linear pde. But if π s is monotone in y then s πts + (a ± βb)πys + 21 b 2 πyy − r πs = 0 π s (t, y ) = ESt [f (y (T ))|y (t) = y ] “Upwind” drift-adjustment into direction of risk A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 13 / 34 Pure Insurance Risk Cost-of-Capital Principle Cost-of-Capital Principle Cost-of-Capital principle, popular by practitioners Used in QIS5-study conducted by EIOPA Idea: hold buffer-capital against unhedgeable risks. Borrow from shareholders by giving “excess return” δ Define buffer via Value-at-Risk measure: h i Πct [f (y (T ))] = Et [f (y (T ))] + δVaRq,t f (y (T )) − Et [f (y (T ))] . A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 14 / 34 Pure Insurance Risk Cost-of-Capital Principle Scaling & PDE Again, pay attention to “time-scaling”: √ First, scale VaR back to per annum basis with 1/ ∆t Then, δ is like interest √ rate,√so multiply with ∆t Net scaling: δ∆t/ ∆t = δ ∆t. Limit: for small ∆t the VaR behaves as Φ−1 (q)×St.Dev. Hence, limiting pde is same as π s but with β = Φ−1 (q)δ. Conclusion: In the limit for ∆t → 0, CoC pricing is the same as st.dev. pricing (for a diffusion process!) A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 15 / 34 Pure Insurance Risk Davis Price Davis Price The variance price π v is “hard” to calculate, the st.dev. price π s is “easy” to calculate Can we make a connection between these two concepts? “Yes, we can!” using small perturbation expansion Consider existing insurance portfolio with price π v (t, y ), now add “small” position with price επ D (t, y ). Subst. into pde: v D (πtv + επtD ) + a(πyv + επyD ) + 12 b 2 (πyy + επyy )+ 2 1 γ (πyv )2 + 2επyv πyD + ε2 (πyD )2 − r (π v + επ D ) = 0 2 X e rt b 0 π v () solves the pde, cancel π v -terms A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 16 / 34 Pure Insurance Risk Davis Price Pricing PDE Simplify pde, and divide by ε: D + πtD + aπyD + 12 b 2 πyy 2 1 γ 2 X e rt b 0 2πyv πyD + ε(πyD )2 − r π D = 0 Approximation: ignore “small” ε-term γ D 2 v D πt + a + b πy πyD + 12 b 2 πyy + r πD = 0 X0 e rt π D (t, y ) = ED t [f (y (T ))|y (t) = y ] Davis price π D is defined only “relative” to existing price π v of insurance portfolio Note, drift-adjustment of st.dev. price scales with b A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 17 / 34 Financial & Insurance Risk Financial & Insurance Risk Investigate environment with financial risk that can be traded (and hedged!) in financial market and non-traded insurance risk Model financial risk as [Black and Scholes, 1973] economy. Model return process xt = ln St under real-world measure P: dx = µ(t, x) − 21 σ 2 (t, x) dt + σ(t, x) dWf Binomial time-step: x(t + ∆t) = x(t) + (µ − A. Pelsser (Maastricht U) 1 2 2 σ )∆t + TC & MC Valuations √ +σ √∆t with P-prob. −σ ∆t with P-prob. 23 May 2013 – ASTIN 1 2 1 2 18 / 34 Financial & Insurance Risk No-arbitrage pricing BS-economy is arbitrage-free and complete ⇔ unique martingale measure Q. No-arbitrage pricing operator for financial derivative F (x(T )): π Q (t, x) = e −r (T −t) EQ t [F (x(T ))] Binomial step for x under measure Q: x(t + ∆t) = x(t) + (µ − 12 σ 2 )∆t+ √ +σ ∆t with Q-prob. √ −σ ∆t with Q-prob. 1 2 1 2 1− 1+ √ µ−r ∆t σ √ µ−r ∆t σ Quantity (µ − r )/σ is Radon-Nikodym exponent of dQ/dP Quantity (µ − r )/σ is also known as market-price of financial risk. A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 19 / 34 Financial & Insurance Risk Quadrinomial Tree Joint discretisation for processes x and y using “quadrinomial” tree with correlation ρ under measure P: State: x + ∆x x − ∆x y − ∆y 1−ρ 4 -% • . & 1−ρ 1+ρ 4 4 y + ∆y 1+ρ 4 Positive correlation increases probability of joint “++” or “−−” co-movement A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 20 / 34 Financial & Insurance Risk Market-Consistent Pricing Market-Consistent Pricing We are looking for market-consistent pricing operators, see e.g. [Malamud et al., 2008] Definition A pricing operator π() is market-consistent if for any financial derivative F (x(T )) and any other claim G (t, x, y ) we have πF +G (t, x, y ) = e −r (T −t) EQ t [F (x(T ))] + πG (t, x, y ). Observation: generalised notion of “translation invariance” for all financial risks A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 21 / 34 Financial & Insurance Risk MC Variance Pricing MC Variance Pricing Intuition: construct MC pricing in two steps using conditional expectations. For full results we refer to [Pelsser and Stadje, 2013]. First: condition on financial risk & use actuarial pricing for “pure insurance” risk γ π v (t +∆t|x±) := E[π v (t +∆t)|x±]+ 12 Var[π v (t +∆t)|x±] r (t+∆t) X0 e v v π++ + 1−ρ π+− 2 2 2 v v Var[π v (t + ∆t)|x+] = 1−ρ π++ − π+− 4 1+ρ v v E[π v (t + ∆t)|x−] = 1−ρ π + π−− −+ 2 2 2 2 v v Var[π v (t + ∆t)|x−] = 1−ρ π−+ − π−− . 4 E[π v (t + ∆t)|x+] = 1+ρ 2 For ρ = 1 or ρ = −1 no unhedgeable risk left ⇒ Var = 0 A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 22 / 34 Financial & Insurance Risk MC Variance Pricing Pricing PDE Second: use no-arbitrage pricing for “artificial” financial derivative π v (t, x, y ) = e −r ∆t EQ [π v (t + ∆t|x±)] √ v ∆t π (t + ∆t|x+) + = e −r ∆t 21 1 − µ−r σ √ µ−r v 1 1 + ∆t π (t + ∆t|x−) 2 σ Do Taylor-expansion & limit ∆t → 0: v πtv + (r − 12 σ 2 )πxv + a − ρb µ−r πy + σ v 2 v 2 v 1 2 v 1 2 v 1 γ 2 σ πxx + ρσbπxy + 2 b πyy + 2 X e rt (1 − ρ )(bπy ) − r π = 0 0 Impact on x: “Q-drift” (r − 12 σ 2 ) Impact on y : adjusted drift a − ρb µ−r σ Non-linear term for “locally unhedgeable variance” (1 − ρ2 )(bπyv )2 A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 23 / 34 Financial & Insurance Risk MC Variance Pricing Pure Insurance Payoff Unfortunately, we cannot solve the non-linear pde in general Special case: consider pure insurance payoff (and constant MPR µ−r σ ), then no (explicit) dependence on x v 1 2 v πy + 2 b πyy + πtv + a − ρb µ−r σ 1 γ 2 X e rt (1 0 − ρ2 )(bπyv )2 − r π v = 0 Note that for ρ 6= 0 the pde is different from the “pure insurance” pde Via correlation with financial market we can still hedge part of the insurance risk Note: incomplete market ⇒ no martingale representation, therefore delta-hedge is not πxv In fact: hold ρbπyv /σ in x as hedge Economic explanation for drift-adjustment in y , a kind of “quanto-adjustment” A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 24 / 34 Financial & Insurance Risk MC Variance Pricing Pure Insurance Payoff (2) General solution via log-transform: # " γ(1−ρ2 ) rt f (y (T )) X e 0 π v (t, y ) = ln EP̃ e X0 e rT y (t) = y γ(1 − ρ2 ) Measure P̃ induces drift-adjusted process for y See also, [Henderson, 2002] and [Musiela and Zariphopoulou, 2004] who derived this solution in the context of exponential indifference pricing We can generalise to Mean Value Principle for any convex function v () A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 25 / 34 Financial & Insurance Risk MC Variance Pricing Numerical Illustration Consider “unit-linked” insurance contract with payoff: y (T )S(T ) = y (T )e x(T ) Numerical calculation in quadrinomial tree with 5 time-steps of 1 year “Naive” hedge is to hold y (t) units of share S(t) In fact: hold πxv + ρbπyv /σ as hedge MC Variance hedge also builds additional reserve as “buffer” against unhedgeable risk Fin Delta t=4 Payoff at T=5 1.00 150.00 0.80 100.00 50.00 0.00 0.50 0.30 0 30 0.10 -0.10 -50.00 -100.00 -150.00 51.88 70.03 -0.30 94.53 127.60 172.25 -0.50 Insurance Risk "y" 0.60 0.40 0.20 0.00 -0.20 -0.40 -0.60 -0.80 -1.00 232.51 Share Price A. Pelsser (Maastricht U) 59.16 0.40 0 40 0.20 0.00 Insurance Risk "y" -0.20 79.85 107.79 Share Price TC & MC Valuations 145.50 -0.40 196.40 23 May 2013 – ASTIN 26 / 34 Financial & Insurance Risk MC Variance Pricing Numerical Illustration (2) Investigate impact of correlation ρ Compare ρ = 0.50 (left) and ρ = 0 (right) Fin Delta t=4 Fin Delta t=4 1.00 1.00 0.80 0.80 0.60 0.40 0.20 0.00 -0.20 -0.40 -0.60 -0.80 -1.00 0.60 0.40 0.20 0.00 -0.20 -0.40 -0.60 -0.80 -1.00 59.16 0.40 0 40 0.20 0.00 Insurance Risk "y" -0.20 79.85 107.79 Share Price 145.50 -0.40 196.40 59.16 0.40 0 40 0.20 0.00 Insurance Risk "y" -0.20 79.85 107.79 Share Price 145.50 -0.40 196.40 Positive correlation leads to higher delta, as this also hedges part of insurance risk: hold πxv + ρbπyv /σ as hedge Price for ρ = 0.00 at t = 0 is e26.75 Price for ρ = 0.50 at t = 0 is e18.79, due to less unhedgeable risk Price for ρ = 0.99 at t = 0 is −e1.98, due to drift-adjustment A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 27 / 34 Financial & Insurance Risk MC Standard-Deviation Pricing MC Standard-Deviation Pricing Again, do two-step construction First: condition on financial risk & use actuarial pricing for “pure insurance” risk √ p π s (t + ∆t|x±) := E[π s (t + ∆t)|x±] + δ ∆t Var[π s (t + ∆t)|x±] Second: do no-arbitrage valuation under Q This leads to linear pricing pde (if π s (t, x, y ) monotone in y ): p 2 b πs + ± δ 1 − ρ πts + (r − 21 σ 2 )πxs + a − ρb µ−r y σ 1 2 s 2 σ πxx s s + ρσbπxy + 12 b 2 πyy − r πs = 0 Drift adjustment for y is now p combination of “hedge cost” plus “upwind” risk-adjustment ±δ 1 − ρ2 b A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 28 / 34 Financial & Insurance Risk MC Davis Price MC Davis Price We can again consider Davis price, by “small perturbation” expansion This leads to pricing pde: πtD + (r − 12 σ 2 )πxD + a − ρb µ−r σ + 1 2 D 2 σ πxx γ X0 e rt (1 − ρ2 )b 2 πyv πyD + D D + ρσbπxy + 21 b 2 πyy − r πD = 0 Drift adjustment for y is now combination of “hedge cost” plus risk-adjustment X0γe rt (1 − ρ2 )b 2 πyv Davis price defined relative to existing price π v (t, x, y ) p Note, st.dev. pricing depends on (1 − ρ2 ) b A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 29 / 34 Financial & Insurance Risk Multi-dimensional MC Variance Price Multi-dimensional MC Variance Price Vectors x of asset returns (n-vector), y of insurance risks (m-vector) 1 dx = µ dt + Σ 2 · dWf 1 dy = a dt + B 2 · dW Partitioned covariance matrix C (n + m) × (n + m) P is n × m matrix of financial & insurance covariances Σ P C= P0 B The market-price of financial risks is an n-vector Σ−1 (µ − r ) Multi-dim pricing pde for π v : 0 πtv + r 0 πxv + a − P 0 Σ−1 (µ − r ) πyv + 12 Cij πijv + v0 0 −1 v v 1 γ π (B − P Σ P)π y y − rπ = 0 2 X e rt 0 Note: (B − P 0 Σ−1 P) is conditional covariance matrix of y |x A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 30 / 34 Financial & Insurance Risk Multi-dimensional MC StDev Price Multi-dimensional MC StDev Price Multi-dim pricing pde for π s : 0 πts + r 0 πxs + a − P 0 Σ−1 (µ − r ) πys + 12 Cij πijs + q 1 δ πys 0 (B − P 0 Σ−1 P)πys − r π s = 0 2 Note: unlike 1-dim case, does not simplify to linear pde Simplification only possible if (B − P 0 Σ−1 P) has rank 1 and all πis have same sign A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 31 / 34 Conclusions Conclusions 1 Pure Insurance Risk Variance Principle (→ exponential indiff. pricing) Standard-Dev. Principle (→ E[] under new measure) Cost-of-Capital Principle (→ St.Dev price) Davis Price: St.Dev. price is “small perturbation” of Variance price 2 Financial & Insurance Risk Market-Consistent Pricing: via two-step conditional expectations MC Variance Principle Numerical Illustration for “unit-linked” contract A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 32 / 34 References References I Black, F. and Scholes, M. (1973). The pricing of options and corporate liabilities. Journal of Political Economy, 81:637–659. Davis, M. (1997). Option pricing in incomplete markets. In Dempster, M. and Pliska, S., editors, Mathematics of Derivative Securities, pages 216–226. Cambridge University Press. El Karoui, N., Peng, S., and Quenez, M. (1997). Backward stochastic differential equations in finance. Mathematical finance, 7(1):1–71. Henderson, V. (2002). Valuation of claims on nontraded assets using utility maximization. Mathematical Finance, 12(4):351–373. A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 33 / 34 References References II Jobert, A. and Rogers, L. (2008). Valuations and dynamic convex risk measures. Mathematical Finance, 18(1):1–22. Malamud, S., Trubowitz, E., and Wüthrich, M. (2008). Market consistent pricing of insurance products. ASTIN Bulletin, 38(2):483–526. Musiela, M. and Zariphopoulou, T. (2004). An example of indifference prices under exponential preferences. Finance and Stochastics, 8(2):229–239. Pelsser, A. and Stadje, M. (2013). Time-consistent and market-consistent evaluations. Mathematical Finance. A. Pelsser (Maastricht U) TC & MC Valuations 23 May 2013 – ASTIN 34 / 34
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