12.07.2015 Views

The Limits of Mathematics and NP Estimation in ... - Chichilnisky

The Limits of Mathematics and NP Estimation in ... - Chichilnisky

The Limits of Mathematics and NP Estimation in ... - Chichilnisky

SHOW MORE
SHOW LESS
  • No tags were found...

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

76 Advances <strong>in</strong> Econometrics - <strong>The</strong>ory <strong>and</strong> Applications30 Will-be-set-by-IN-TECHcomplex adjustments to the model were <strong>of</strong>ten required to account for potential problemsrelated to stock sampl<strong>in</strong>g <strong>and</strong> <strong>in</strong>itial conditions. Fortunately, we were able to avoid thesedifficulties by recreat<strong>in</strong>g each <strong>in</strong>dividual’s history as early as age 16, the legal school-leav<strong>in</strong>gage <strong>in</strong> Canada. Consequently, the <strong>in</strong>itial state can be safely considered exogenous, <strong>and</strong> thesubsequent duration times void <strong>of</strong> any form <strong>of</strong> bias.<strong>The</strong>re is no consensus <strong>in</strong> the literature concern<strong>in</strong>g the appropriate treatment <strong>of</strong> unobservedheterogeneity <strong>in</strong> multi-states multi-episodes duration models. When few states areconsidered, two-factor load<strong>in</strong>g models with a f<strong>in</strong>ite set <strong>of</strong> po<strong>in</strong>ts <strong>of</strong> support have becomerelatively st<strong>and</strong>ard. When the analysis focuses on more states, factor load<strong>in</strong>g models require alarge number <strong>of</strong> parameters to be flexible or become relatively restrictive if a parsimoniousspecification is used. In this chapter we have chosen to <strong>in</strong>vestigate the sensitivity <strong>of</strong> theparameter estimates by compar<strong>in</strong>g a typical non-parametric specification <strong>and</strong> a series <strong>of</strong>parametric two-factor load<strong>in</strong>g models. <strong>The</strong>se models implicitly assume that the <strong>in</strong>tensity<strong>of</strong> transitions are related to the state <strong>of</strong> dest<strong>in</strong>ation. We have also estimated a parametricthree-factor load<strong>in</strong>g model. <strong>The</strong> novelty <strong>of</strong> this specification lies <strong>in</strong> the fact that the <strong>in</strong>tensities<strong>of</strong> transitions are related to both to the state <strong>of</strong> dest<strong>in</strong>ation <strong>and</strong> the state <strong>of</strong> orig<strong>in</strong>.<strong>The</strong> estimation <strong>of</strong> the model yields a number <strong>of</strong> <strong>in</strong>terest<strong>in</strong>g results. As found <strong>in</strong> previousstudies, unobserved heterogeneity appears to play an important role <strong>in</strong> determ<strong>in</strong><strong>in</strong>g whoselects or gets selected <strong>in</strong> tra<strong>in</strong><strong>in</strong>g programs. On the other h<strong>and</strong>, the slope <strong>and</strong> basel<strong>in</strong>e hazardparameter estimates are not very sensitive to the choice <strong>of</strong> a particular distribution functionfor the unobserved heterogeneity variables. <strong>The</strong> two-factor load<strong>in</strong>g models, either parametricor non-parametric, yield essentially the same results as the three-factor load<strong>in</strong>g model. <strong>The</strong>seshow that the duration times <strong>in</strong> any <strong>of</strong> the seven states considered are sensitive to variations<strong>in</strong> program parameters such as welfare benefits, policy variables such as the m<strong>in</strong>imum wagerate, <strong>and</strong> <strong>in</strong> the economic environment as proxied by the unemployment rate. Nearly all theparameter estimates have the expected sign when statistically significant.<strong>The</strong> results perta<strong>in</strong><strong>in</strong>g to the impact <strong>of</strong> the welfare tra<strong>in</strong><strong>in</strong>g programs <strong>and</strong> JRP are similarto those found earlier by Gritz (1993), Bonnal et al. (1997) <strong>and</strong> Fort<strong>in</strong> et al. (1999a). Inessence, young, poorly educated males who participate <strong>in</strong> these programs do not fair as wellon the labour market compared to non-participants, even after controll<strong>in</strong>g for unobservedheterogeneity. On the other h<strong>and</strong>, participation <strong>in</strong> tra<strong>in</strong><strong>in</strong>g programs while on unemployment<strong>in</strong>surance provides them some benefits <strong>in</strong> the form <strong>of</strong> <strong>in</strong>creased transitions <strong>in</strong>to employment.6. ReferencesBeaudry, P. & Green, D. A. (2000). Cohort patterns <strong>in</strong> canadian earn<strong>in</strong>gs: assess<strong>in</strong>g the role <strong>of</strong>skill premia <strong>in</strong> <strong>in</strong>equality trends, Canadian Journal <strong>of</strong> Economics 33: 907–936.Blasco, S., Crépon, B. & Kamionka, T. (2009). Evaluation <strong>of</strong> the Impact <strong>of</strong> Tra<strong>in</strong><strong>in</strong>g on IndividualLabor Market Transitions, Mimeo, Crest, Paris.Bonnal, L., Fougère, D. & Sér<strong>and</strong>on, A. (1997). Evaluat<strong>in</strong>g the impact <strong>of</strong> french employmentpolicies on <strong>in</strong>dividual labour market histories, <strong>The</strong> Review <strong>of</strong> Economics Studies64(4): 683–718.Brouillette, D. & Lacroix, G. (2010). Heterogeneous treatment <strong>and</strong> self-selection <strong>in</strong> a wagesubsidy experiment, Journal <strong>of</strong> Public Economics 94(7-8): 479 – 492.Brouillette, D. & Lacroix, G. (2011). Assess<strong>in</strong>g the impact <strong>of</strong> a wage subsidy for s<strong>in</strong>gle parentson social assistance <strong>in</strong> canada, Canadian Journal <strong>of</strong> Economics, Forthcom<strong>in</strong>g.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!