Info-Metrics: Theory and Applications Department of Economics - American University Campus Washington DC, September 24-25 2010 GME ESTIMATION WITH NON-LINEARITIES AND SPATIAL DEPENDENCE IN CLUB CONVERGENCE ACROSS OECD COUNTRIES Rossella Bernardini Papalia*, Silvia Bertarelli^ *Department of Statistics, University of Bologna, Italy, [email protected] ^Department of Economics, University of Ferrara, Italy, [email protected] 1 MOTIVATIONS Empirical evidence on regional convergence suggests that regions and countries are not homogenous and not independent units. It is necessary to incorporate heterogeneity by making a further distinction between the concepts of absolute location (spatial heterogeneity) and relative location (spatial dependence) 1. Absolute location refers to the impact of being located at a particular point in space. 2. Relative location considers relevant the position of a region relative to other regions. From a theoretical perspective as suggested by Masanjala and Papageorgiou (2004) heterogeneity is strictly connected with non linearities. Spatial externalities may be introduced in theoretical growth models yielding convergence equations with spatial autocorrelation. 2 ESTIMATION PROBLEMS Estimation of models incorporating spatial heterogeneity poses both identification and collinearity problems (omitted variable bias; correlation between unobserved heterogeneity -individual specific effects- and explanatory variables). In the presence of residual regional heterogeneity, estimation of convergence models poses -SPECIFIC PROBLEMS: 1. identification problems; 2. endogeneity/collinearity problems; 3. omitted variables related to initial conditions; 4. simultaneity 5. incidental parameter problem, short panels, spatial and time period fixed effects. As a consequence: the standard estimation procedures employed in many studies can produce biased estimates (and/or with large variances) of the convergence rate. ML-based estimation techniques (Anselin, 1988) Groups and a nonparametric covariance estimation technique, GMM (Driscoll at al., 1998), Feasible GLS procedures, two stages procedures; estimated GLS (EGLS) (Baltagi, 2006; Kelejian and Prucha, 1998, 1999), MCMC methods (Kakamu et al., 2006) introduction of prior restrictions on the parameters to reduce the dimensionality of the problem. 3 OBJECTIVES ‐ to develop a two stage strategy to estimate a spatial club convergence model which introduces: (i) (ii) (iii) non linearities; information on clustering schemes identified by a mapping analysis; a GME estimation procedure AT THE FIRST STAGE: We introduce spatial heterogeneity (absolute location effects) The spatial dependence is incorporated into the model by specifying a dynamic spatial model In spatial process models, one proceeds by specifying the spatial process and by choosing an appropriate spatial weights matrix that must not contain any of the exogenous or endogenous variables used in the growth regression. We assume 1. non linearities 2. different TFPs 3. statial autocorrelation Clubs are identified by means of a mapping analysis. 4 AT THE SECOND STEP The objective is to incorporate spatial effects and/or externalities into the regimes specification. The growth analysis is extended to take account of relative location effects by explicitly modeling spatial dependence (residual heterogeneity) within clubs. We specify a multi-club spatial convergence model, with clubs corresponding to subsets of regions, which are identified at the first stage of the analysis. APPLICATION The proposed strategy is applied to assess the existence of club convergence across OECD countries over the period 1965-2004. The case of OECD countries gives us the possibility to contribute to a debate on the identification of clubs across a small sample of countries whose results are still ambiguous. 5 ECONOMIC BACKGROUND (1) GROWTH MODELS WITH HETEROGENEOUS PARAMETERS Heterogeneity is strictly connected with non linearities. From a theoretical perspective non linearities may be connected with the internal sources of factor accumulation (Peretto, 1999), could be the result of different adoption speeds of technological spillovers (Parente and Prescott 1994), the evolution of one economy might be path dependent so that different initial conditions induce the choice of different technologies (Ciccone and Matsuyama, 1996; Galor and Zeira, 1993) or technology is CES (Masanjala and Papageorgiou, 2004). Non linear growth processes imply multiple steady states. Multiple equilibria may be generated by the presence of threshold externalities of accumulated factors (Azariadis and Drazen, 1990) and cross country differences in the level of financial development (Acemoglu and Zilibotti, 1997). From an empirical perspective, the pioneering work of Durlauf and Johnson (1995) has empirically studied multiple development clubs and growth regimes, accounting for parameter heterogeneity and implying that different countries obey different linear growth processes. Several subsequent papers have shown significant non linearities for a variety of variables (Mamuneas et al., 2006; Ketteni et al., 2007). 6 ECONOMIC BACKGROUND (2) GROWTH MODELS WITH SPATIAL CORRELATION Spatial externalities may be introduced in theoretical growth models yielding convergence equations with spatial autocorrelation From a theoretical perspective, models of endogenous growth often emphasize the importance of technological, physical and human capital spillovers. Such spillovers are connected to i) human capital and institutional differentials ii) bilateral channels such as trade and foreign direct investment (Coe et al., 1995; Keller, 1998). The magnitude of these spillovers depends on the patterns of spatial interdependence among regions Growth models with spillovers arising from geographical proximity have been derived by Lopez-Bazo et al. (2004), Ertur and Koch (2007). The interest in location and economic growth issues has led the economists of the New Economic Geography to include explicit mechanism of geographical agglomeration in endogenous growth models (Martin and Ottaviano 2001, Fujita and Thisse 2002). From an empirical perspective, the empirical evaluation of spatial dependence in convergence processes has been implemented at regional level by Ertur et al. (2006) and Ertur and Koch (2007) among others. 7 STEP I – PROCEDURE: IDENTIFICATION OF CONVERGENCE CLUBS BY A MAPPING STRUCTURE A mapping structure is introduced in the dynamic optimization problem to investigate unobserved heterogeneity. The approach aims at investigating regional spatial heterogeneity by also capturing the contribution of omitted variables such as the unobserved quality of institutions, and the unobserved determinants of regional technological and structural characteristics. Advantages: 1. to allow for an endogenous selection of regional clusters 2. to facilitate the interpretation of the cluster outcomes, providing a measure of the role (weight) of different unobserved dimensions. 8 THE LOCATION MAP OF UNOBSERVED VARIABLES As in the choice map, the position of the unobserved variables on the M-dimensional map and the weights for these dimensions are derived. The resulting location map can be obtained by using a two stage process: First, the parameters of the growth model are estimated and the covariance matrix of unobserved components i ’s is computed. Then this matrix is used as an input in multidimensional scaling to obtain their locations in a multi-attribute space. We assume that the time-invariant effect, i , is a linear function of the country’s time invariant attributes which lie within a two-dimension map, such as: i s1l1 s2l2 i (s1 , s2) are parameters modeled as a function of country’s characteristics; (l1 , l2) are the coordinates representing the location of the unobserved effect on the map (to be estimated); i is a random error with zero mean. This procedure endogenously identifies the determinants of TFP differences. The interpretation of the dimensions of the map (l1i, l2i) is driven by growth theory and may capture the contribution of national unobserved variables such as the quality of institutions, and the distance matrix. 9 MODEL SPECIFICATION We start by specifying a dynamic panel model with country fixed effects as follows: ln y ln y 'D t u (1) it it 1 it 1 i it 5-year average data: all data are expressed in logs and are calculated as 5-year averages to eliminate the business cycle component. ln yit-1 refers to the endogenous lagged per capita GDP level, Time effects control for the presence of a time trend component and of a common stochastic trend (the common component of technology). Individual effects capture total factor productivity (TFP) differences, and other time-invariant omitted variables (correspond to initial conditions for technological characteristics and institutions and strongly influence the formation of clubs). Explanatory variables suggested by theory to approximate the steady state output are (in logs): the vector Dit-1 of country-specific explanatory variables includes skit-1 the investment rate in physical capital, ndxit-1 the sum of the population growth rate, the exogenous technological growth rate, and the depreciation rate (gives the determinants of the steady state output and consists of a set of country-specific explanatory variables suggested by the theory). Additional country-specific control variables that influence both the steady state output and total factor productivity (TFP) levels: variables capturing technological and geographical spillovers. 10 Fixed effects in Dynamic spatial panel models: Panel models give us the advantage of introducing and estimating fixed effects in the conditional convergence model to identify convergence clubs and to allow for spatial unobserved heterogeneity among spatial units. Spatial dependence effects capture pecuniary and technological spillovers since they are connected to geographical distance between country pairs. The Dynamic models for Spatial Panel models exhibiting both dependence in the dependent variable and the error structure y I W y X u N T u W u N E ' 2 I NT with y as a NT×1 vector, X as a NT×K matrix and parameter, and the other notation is as before. as a NT×1 vector, is the scalar spatial autoregressive The set of k explanatory variables X is enlarged to include the spatial lagged dependent variables lnyit-1 and country and time fixed effects ( X ln yiy 1 T I N I T N ); is the Kronecker product operator, T and N are T×1 and N×1 vectors of all unity elements respectively, and IN and IT are identity matrices of dimension N and T, respectively. 11 When the spatial autocorrelation is modeled by a spatial autoregressive process in the error terms we refer to SPATIAL ERROR MODEL -SEM MODEL is the parameter associated to the spatially lagged error term 1. it is observed how a random shock in a region affects growth rates in that region and additionally impacts all the other regions through the spatial transformation 2. the presence of global externalities are associated solely with random shocks (they measure the joint effect of misspecification, omitted variables, and spatial autocorrelation). When the spatial autocorrelation is modeled by a SPATIAL LAG MODEL, SPATIAL AUTOREGRESSIVE MODEL – SAR MODEL we have: is the parameter associated to the spatially lagged dependent variable WY the spatial interaction effect indicate the degree to which the growth rate of per-capita GDP in one region is determined by the growth rates of its neighboring regions. 1. all spatial dependence effects are captured by the lagged term. 2. It is observed how the performance of the dependent variable impacts all the other (neighbor) regions through the spatial transformation 3. the presence of global spillovers is associated to GDP growth rates. One proceeds by testing the null hypotheses (ML and LM based tests, Anselin, 1992): H0: =0; SEM H0: ρ =0; SAR 12 Spatial weights are derived from the location and spatial arrangements of observation by means of a geographic information system. Regions are defined ‘neighbors’ when they are within a given distance of each other, i.e. wij =1 for d ij and ij, where dij is the great circle distance between the capital cities of region i and j, is a critical cut-off value (distance-based contiguity), above which all interactions are assumed to be negligible. More specifically, a spatial weights matrix W* is defined as follow: 0 if w 1 if 0 if * ij i j d ij ,i j . dij , i j The elements of the row-standardized spatial weights matrix W (with elements of a row sum to one) result: wij wij* N w j 1 13 * ij , i, j 1,.., N . ESTIMATION_GME We introduce a GME formulation which produces consistent parameter estimates of a conditional convergence model in presence of collinearity and endogeneity of lagged dependent variable, spatial lag variables, and some explanatory variables such as fiscal policy and openness. This technique is here suggested with the aim of correcting for biases: (i) connected to model specification problems (omitted variable bias), (ii) arising from simultaneity, miss-specified dynamics and/or measurement errors. It is suggested: (i) in presence of small samples, when the number of time periods, T, is not sufficiently large, (ii) when the number of regions N is greater than the number of time periods, T (N>T); (iii) in presence of collinearity and/or endogeneity of explanatory variables. 14 The coefficients are all Re-Parameterized as expected values of discrete random variable with M fixed points for the coefficients and J for the errors. The Re-Parameterized coefficients are defined as follows == Z = p ; = Z p ; = Z p ; u= V u r u ; = V r . is enlarged to include time and fixed effects. The matrices (Z, Z, Z) and (Vu, Vε) define the support fixed points for the re-parameterization of the coefficients and the error terms. The coefficients and the error terms are estimated by recovering the probability distribution of the discrete random variables set. The vectors p=vec(p p pρ) and r=vec(ru, r ) are vectors of proper probability distributions for parameters and errors, respectively, while p, p, p, rε, ru, are calculated by the maximization the traditional entropy function subjected to the following consistency and adding-up constraints. The consistency constraint represents the information about the data expressed by the reformulated model in the equation: Y Z p I W Y X Z p Z p W V u r u V r ; N T N The adding-up constraints impose that the sum of each coefficients and the error terms probability vector have to be equal to 1. 15 STEP II - PROCEDURE: SPECIFICATION OF THE SPATIAL MULTIPLE REGIMES MODEL Clubs correspond to subsets of regions identified by means of the mapping analysis. Each club may be represented by a cross-sectional equation. Spillovers connected to geographical distance are modelled in terms of spatial dependence effects. We consider a system of two equations, one for each regime, the two-club growth model can be modelled assuming a LAG functional form or SEM functional form. Consistent and asymptotically normal estimates may be obtained by using the generalized maximum entropy (GME) estimation approach. 16 CLUB CONVERGENCE, THRESHOLD EXTERNALITIES AND SPATIAL DEPENDENCE ANALYSIS FOR OECD COUNTRIES Step I procedure: identification of clubs ‐ Pooled OLS estimates display spatial heterogeneity, heteroskedasticity, non normality and collinearity (TABLE 1) ‐ Having proved the existence of endogeneity for ln yit-1 and shit-1, as well as collinearity, the generalized maximum entropy approach has been employed. ‐ parameter estimates for a mixed model with both spatial lag and spatial error components ‐ Multi dimensional scaling of time invariant country specific effects, used to measure initial TFP levels Results: 2 clubs of OECD countries emerge in accordance with Canova (2004) Country groupings are different from Canova (2004). Club 1 comprises 15 countries, while Australia, Italy, Korea, Mexico, Portugal, Spain, Switzerland and Turkey join club 2 (table 2) Determinants of TFP levels (scatter plot analysis): good institutions and high quality human capital are positively correlated with one dimension. 17 Step II procedure: differences in growth determinants across clubs ‐ GME estimates of a system of two convergence equations, for both spatial SEM and spatial LAG models ‐ The Wald test on the homogeneity of the parameters across equations points out to the superiority of a specification with heterogeneous slope coefficients. ‐ Since the LM Lag test value exceeds the LM Error test value, the two tests point to the presence of spatial lag dependence rather than spatial error autocorrelation. Results: With reference to spatial dependence, per capita GDP in a country is positively affected by neighboring countries’ GDP within each club. In addition, these complementarity effects are different across regimes (stronger in club 2 countries than in club 1 ones). With reference to interaction terms (threshold externalities), the non-monotonic pattern of convergence is strongly influenced by human capital stocks. In club 1, significant non linear effects of primary and secondary attainment emerge. In club 2, primary and tertiary attainment levels show significant coefficients with opposite signs. With reference to club convergence determinants, a link between stages of development and returns to physical capital and levels of education emerges: club 2 shows the highest returns of physical capital and primary average years of schooling, while the highest return on secondary average years of schooling is related to club 1. Tertiary school attainment shows negative effects in club 2, while club 1 coefficient is not significant. 18 RESULTS • Our results strongly support the presence of TFP heterogeneity across OECD COUNTRIES in the 19652004 period. • The key role of both technology spillovers through human capital accumulation and non linearities (interaction terms, threshold externalities )has been confirmed by our results. • First step results: 1. two clubs are identified 2. presence of mixed spatial correlation and non linearities. • Second step results: 1. Our analysis, while confirming the convergence club hypothesis across OECD COUNTRIES in the 1965-2004 period, has shown the presence of spatial lag dependence. The global externalities are not associated with random shocks, but neighbors’ growth rates tend to positively influence the economic performance of a region (LAG model). 2. Results consistent with analyses based on a large sample of countries (72 countries, with all OECD countries) We find four clubs: OECD countries are in clubs 1 and 2 (only Turkey is in club 3). Club 1 in the OECD sample coincides with club 1 in the large sample, with the exception of Italy, Australia (reported in club 2 in the OECD sample analysis and in club 1 in the large sample one) and Greece (reported in club 1 in the OECD sample analysis and in club 2 in the large sample one). With reference to growth determinants, our OECD results are confirmed. The convergence process is different across regimes, threshold externalities are important and different returns on factor accumulation emerge. 19 FURTHER INVESTIGATION should be done in order to: to compute TFP levels without imposing stationarity FURTHER RESEARH Spatial weights Matrix: Economic distance, semi-parametric, entropy based estimation; Computational vs statistical efficiency Spatial panels: separability vs non-stationarity 20 Table 1: Pooled OLS estimates Tests (p-values) Tests for heteroskedasticity: Variables ln yit-1 Estimation results 0.784*** ndxit-1 -0.078 1) Breusch-Pagan test skit-1 0.060** 2) White test°° Education primary -0.370 Tests for normality: 1) Skewness and kurtosis of residuals° 2) Information Matrix test Education secondary Education tertiary -0.400 0.266 Financial development 0.371** - Skewness°° Openness Fiscal expenditure Inflation 0.024* -0.022 0.524*** - Kurtosis°° Rate of convergence Adj. R2 RMSE 21 1.02 (0.386) 32.32 (0.029) 6.38 (0.012) Autocorrelation of residuals°°° 0.214*** - Lag 2 0.041 0.042 -0.020 - Lag 3 3.76 (0.0002) 1.31 (0.192) 0.11 (0.909) AIC BIC N. obs. -392.71 -334.17 138 - Lag 1 Edu tert * Fin dev Lagged dep var * edu prim Lagged dep var * edu sec Lagged dep var * edu tert 8.59 (0.003) 138 (0.46) VARIABLE 0.9845 0.0546 Table 2: Step I GME estimates Variables ln yit-1 ndxit-1 skit-1 Education primary Education secondary Education tertiary Financial development Openness Fiscal expenditure Inflation Edu tert * Fin dev Lagged dep var * edu prim Lagged dep var * edu sec Lagged dep var * edu tert Spatial dep. variable Spatial error Rate of convergence Adj. R2 RMSE 22 Std. Coefficient Error 0.825 0.000002 -0.008 0.00003 0.004 0.00004 0.167 0.0016 0.026 0.0028 -0.002 0.0009 -0.007 0.0008 0.004 0.0001 0.016 0.0001 0.001 0.0002 0.004 0.0008 0.018 0.002 -0.0004 0.103 0.00003 0.0002 0.0003 0.0001 0.0006 0.00001 VARIABLE 0.9639 N. obs. 0.0684 P-value <.0001 <.0001 <.0001 <.0001 <.0001 0.012 <.0001 <.0001 <.0001 0.002 <.0001 <.0001 <.0001 0.000 <.0001 <.0001 138 Table 3: OECD country groupings Club Club AUS 1 2 Australia AUT Austria CHE BEL Belgium Switzerland CAN Canada ESP Spain DNK Denmark ITA Italy FIN Finland KOR Korea MEX FRA France Mexico PRT Portugal GBR Great Britain TUR GER Germany Turkey GRC Greece IRL Ireland JPN Japan NLD Netherlands NOR Norway SWE Sweden USA United States of America 23 Table 4: Step II GME estimates, OECD countries (1965-2004) Club 1 Club 2 Std. PStd. Variables Coefficient Error value Coefficient Error ln yit-1 0.964 0.0008 <.0001 0.855 0.0008 ndxit-1 -0.021 0.0003 <.0001 -0.040 0.0002 skit-1 0.002 0.00002 <.0001 0.020 0.0001 Education primary 0.059 0.001 <.0001 0.314 0.001 Education secondary 0.015 0.004 0.000 0.006 0.003 Education tertiary -0.003 0.003 0.340 -0.019 0.001 Financial development -0.002 0.0002 <.0001 -0.055 0.007 Openness 0.001 0.00004 <.0001 0.009 0.00003 Fiscal expenditure 0.010 0.0001 <.0001 0.009 0.0001 Inflation 0.0004 0.0001 0.002 0.001 0.0001 Edu tert * Fin dev 0.0004 0.001 0.572 0.032 0.005 Lagged dep var * edu prim 0.008 0.0002 <.0001 0.026 0.0003 Lagged dep var * edu sec 0.001 0.0003 0.005 -0.000001 0.0002 Lagged dep var * edu tert -0.0004 0.0002 0.089 -0.001 0.00004 Spatial dep. variable 0.004 0.0001 <.0001 0.007 0.00004 24 Pvalue <.0001 <.0001 <.0001 <.0001 0.033 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 <.0001 0.997 <.0001 <.0001 Table 5: Country groupings, Durlauf and Johnson (1995) sample Club Club Club Club 1 2 3 4 AUS AUT BEL CAN DNK FIN FRA GBR GER IRL ISR ITA JPN NLD NOR SWE USA 25 Australia Austria Belgio Canada Denmark Finland France United Germany Ireland Israel Italy Japan Netherlands Norway Sweden United ARG CHE CHL CRI ECU EGY ESP GRC KOR MEX PAN PHL PRT URY VEN Argentina Switzerland Chile Costa Rica Ecuador Egypt Spain Greece Korea Mexico Panama Philippines Portugal Uruguay Venezuela BGD BOL BRA COL DZA GTM HND IDN IND JAM JOR LKA MAR MUS MYS PAK PER PRY SLV THA TUN TUR Bangladesh Bolivia Brazil Colombia Algeria Guatemala Honduras Indonesia India Jamaica Jordan Sri Lanka Morocco Mauritius Malaysia Pakistan Peru Paraguay El Thailand Tunisia Turkey CIV CMR ETH GHA HTI KEN MDG MLI MWI NGA RWA SDN SEN SGP SLE UGA ZAR ZMB ZWE Cote Cameroon Ethiopia Ghana Haiti Kenya Madagascar Mali Malawi Nigeria Rwanda Sudan Senegal Singapore Sierra Uganda Congo Zambia Zimbabwe Table 6: Step II GME estimates, Durlauf and Johnson (1995) sample Club 1 Club 2 Std. PStd. PVariables Coefficient Error value Coefficient Error value ln yit-1 0.899 0.001 <.0001 0.801 0.001 <.0001 ndxit-1 -0.007 0.00001 <.0001 -0.101 0.0002 <.0001 skit-1 0.002 0.00001 <.0001 0.001 0.000003 <.0001 Education primary 0.174 0.001 <.0001 0.357 0.002 <.0001 Education secondary 0.036 0.002 <.0001 -0.003 0.002 0.072 Education tertiary -0.003 0.0005 <.0001 -0.023 0.001 <.0001 Financial development -0.003 0.0002 <.0001 -0.005 0.0001 <.0001 Openness 0.001 0.000004 <.0001 0.001 0.000003 <.0001 Fiscal expenditure 0.013 0.0001 <.0001 0.008 0.00003 <.0001 Inflation 0.0001 0.00001 <.0001 0.000 0.00001 <.0001 Edu tert * Fin dev 0.001 0.0003 <.0001 0.002 0.0001 <.0001 Lagged dep var * edu prim 0.013 0.00002 <.0001 0.035 0.0002 <.0001 Lagged dep var * edu sec 0.002 0.0002 <.0001 -0.001 0.0002 <.0001 Lagged dep var * edu tert -0.0003 0.00004 <.0001 -0.003 0.0001 <.0001 Spatial dep. variable 0.004 0.00001 <.0001 0.009 0.00002 <.0001 26 Table 6 (continue): Step II GME estimates, Durlauf and Johnson (1995) sample Club 3 Club 4 Std. PStd. PVariables Coefficient Error value Coefficient Error value ln yit-1 0.917 0.001 <.0001 0.949 0.001 <.0001 ndxit-1 -0.040 0.00006 <.0001 -0.005 0.00001 <.0001 skit-1 0.005 0.00001 <.0001 0.001 0.000002 <.0001 Education primary 0.027 0.0004 <.0001 0.016 0.0004 <.0001 Education secondary -0.004 0.001 <.0001 -0.015 0.001 <.0001 Education tertiary -0.010 0.0002 <.0001 -0.007 0.0001 <.0001 Financial development -0.002 0.00003 <.0001 -0.004 0.00004 <.0001 Openness 0.001 0.000002 <.0001 0.004 0.00001 <.0001 Fiscal expenditure 0.004 0.00001 <.0001 0.002 0.00001 <.0001 Inflation -0.001 0.00001 <.0001 0.000 0.000003 <.0001 Edu tert * Fin dev 0.002 0.0001 <.0001 0.001 0.00001 <.0001 Lagged dep var * edu prim 0.002 0.00005 <.0001 0.001 0.00004 <.0001 Lagged dep var * edu sec -0.001 0.0001 <.0001 -0.003 0.0001 <.0001 Lagged dep var * edu tert -0.002 0.00004 <.0001 -0.002 0.00002 <.0001 Spatial dep. variable 0.012 0.00003 <.0001 0.010 0.00002 <.0001 27 The case of OECD countries gives us the possibility to contribute to a debate on the identification of clubs across a small sample of countries whose results are still ambiguous. Results of previous studies of convergence for OECD countries indicate some potential puzzles: - Early studies (Barro, 1991; Mankiw et al., 1992; among others) have found evidence of absolute convergence for OECD countries. - Within the time series approach, Bernard and Durlauf (1995) reject convergence hypothesis of OECD countries using standard univariate and multivariate time series techniques and find more than one common long run factor. Andres and Bosca 2000) identify two different groups within the OECD, with significantly different technologies. Nahar and Inder (2002) find evidence of convergence of OECD countries towards USA per capita GDP, regarded as the closest proxy of steady state output. - Canova (2004) applies a Bayesian technique to find two clubs for OECD countries using initial income as a mean to order and group countries. For a large sample of countries (OECD included) - Durlauf and Johnson (1995) have empirically studied multiple development clubs and growth regimes, accounting for parameter heterogeneity and implying that different countries obey different linear growth processes. They use initial income per capita to identify clubs and then estimate a (linear) conditional convergence equation for each club - Several subsequent papers have shown significant non linearities for a variety of variables (Mamuneas et al., 2006; Ketteni et al., 2007). In addition, Tan (2009) has used information on the interactions between covariates, to account for threshold externalities such as the model of Azariadis and Drazen (1990). 28
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