Semiparametric Efficiency Bound for Models of Sequential Moment Restrictions Containing Unknown Functions

This paper computes the semiparametric efficiency bound for finite dimensional parameters identified by models of sequential moment restrictions containing unknown functions. Our results extend those of Chamberlain (1992b) and Ai and Chen (2003) for semiparametric conditional moment restriction models with identical information sets to the case of nested information sets, and those of Chamberlain (1992a) and Brown and Newey (1998) for models of sequential moment restrictions without unknown functions to cases with unknown functions of possibly endogenous variables. Our bound results are applicable to semiparametric panel data models and semiparametric two stage plug-in problems. As an example, we compute the efficiency bound for a weighted average derivative of a nonparametric instrumental variables (IV) regression, and find that the simple plug-in estimator is not efficient. Finally, we present an optimally weighted, orthogonalized, sieve minimum distance estimator that achieves the semiparametric efficiency bound.Sequential moment models, Semiparametric efficiency bounds, Optimally weighted orthogonalized sieve minimum distance, Nonparametric IV regression, Weighted average derivatives, Partially linear quantile IV

Semiparametric efficiency bound for models of sequential moment restrictions containing unknown functions

This paper computes the semiparametric efficiency bound for finite dimensional parameters identified by models of sequential moment restrictions containing unknown functions. Our results extend those of Chamberlain (1992b) and Ai and Chen (2003) for semiparametric conditional moment restriction models with identical information sets to the case of nested information sets, and those of Chamberlain (1992a) and Brown and Newey (1998) for models of sequential moment restrictions without unknown functions to cases with unknown functions of possibly endogenous variables. Our bound results are applicable to semiparametric panel data models and semiparametric two stage plug-in problems. As an example, we compute the efficiency bound for a weighted average derivative of a nonparametric instrumental variables (IV) regression, and find that the simple plug-in estimator is not efficient. Finally, we present an optimally weighted, orthogonalized, sieve minimum distance estimator that achieves the semiparametric efficiency bound.

Semiparametric Efficiency Bound for Models of Sequential Moment Restrictions Containing Unknown Functions

This paper computes the semiparametric efficiency bound for finite dimensional parameters identified by models of sequential moment restrictions containing unknown functions. Our results extend those of Chamberlain (1992b) and Ai and Chen (2003) for semiparametric conditional moment restriction models with identical information sets to the case of nested information sets, and those of Chamberlain (1992a) and Brown and Newey (1998) for models of sequential moment restrictions without unknown functions to cases with unknown functions of possibly endogenous variables. Our bound results are applicable to semiparametric panel data models and semiparametric two stage plug-in problems. As an example, we compute the efficiency bound for a weighted average derivative of a nonparametric instrumental variables (IV) regression, and find that the simple plug-in estimator is not efficient. Finally, we present an optimally weighted, orthogonalized, sieve minimum distance estimator that achieves the semiparametric efficiency bound

Inefficacité marshallienne, partage de coûts et modèles contractuels avec marchés manquants : Résultats empiriques tunisiens

En présence de risque moral, la théorie des contrats prédit que le métayage sera assujetti au problème de l’inefficacité marshallienne, ce qui veut dire que les métayers utiliseront des quantités d’intrants différents sur les terres qu’ils exploitent par opposition aux propriétaires exploitants. Dans cet article, nous examinons cette question à l’aide d’une base de données unique en son genre collectée en 1993 dans le village tunisien d’El Oulja, grâce au financement du programme PARADI. Nous examinons quatre questions jusqu’à présent ignorées par les chercheurs : (1) le partage des coûts entre propriétaires et tenanciers; (2) les intrants en gestion fournis par les propriétaires; (3) la supervision des tenanciers par les propriétaires; (4) l’interaction répétée entre propriétaires et tenanciers. Nous utilisons des méthodes économétriques en panel avec effets fixes et en tobit en utilisant la méthode du trimmed LAD proposée par Honoré (1992). Nos résultats empiriques appuient l’argument selon lequel le risque moral est présent dans les relations contractuelles dans ce village. Par contre, l’importance quantitative des termes des contrats dans la détermination de l’utilisation des intrants, ainsi que de l’output, est relativement limitée. Il s’ensuit que le métayage est probablement choisi pour des raisons autres que le risque moral, telles que le partage du risque ou les coûts de transaction.When moral hazard concerns are present, standard contract theory predicts the "Marshallian inefficiency" of sharecropping contracts, in the sense that, ceteris paribus, sharecropping tenants will use different amounts of inputs than owner operators. In this paper, we examine this issue using a unique dataset collected in 1993 in the Tunisian village of El Oulja, thanks to the financial support of the PARADI program. We focus our attention on four questions that have been neglected by previous studies, namely: (1) cost sharing between landlords and tenants; (2) management inputs provided by landlords; (3) direct supervision of tenants by landlords; (4) repeated interaction between landlords and tenants. We implement panel estimation with household-specific fixed effects and control for the censoring of the dependent variable using the trimmed LAD estimator proposed by Honoré (1992). Our empirical results show that moral hazard is indeed an issue in tenancy contracts in the village, but that its quantitative importance in determining input use, in comparison with other factors, is relatively small. It follows that sharecropping is probably not chosen because of moral hazard concerns, and that other motivations, such as risk sharing or transaction costs, may be more important determinants of contractual choice

Standard errors for the retransformation problem with heteroscedasticity.

Abstract Economists often estimate models with a log-transformed dependent variable. The results from the log-transformed model are often retransformed back to the unlogged scale. Other studies have shown how to obtain consistent estimates on the original scale but have not provided variance equations for those estimates. In this paper, we derive the variance for three estimates -the conditional mean of y, the slope of y, and the average slope of y -on the retransformed scale. We then illustrate our proposed procedures with skewed health expenditure data from a sample of Medicaid eligible patients with severe mental illness.

Advertising Bans and the Substitutability of Online and Offline Advertising

The authors examine whether the growth of the Internet has reduced the effectiveness of government regulation of advertising. They combine nonexperimental variation in local regulation of offline alcohol advertising with data from field tests that randomized exposure to online advertising for 275 different online advertising campaigns to 61,580 people. The results show that people are 8% less likely to say that they will purchase an alcoholic beverage in states that have alcohol advertising bans compared with states that do not. For consumers exposed to online advertising, this gap narrows to 3%. There are similar effects for four changes in local offline alcohol advertising restrictions when advertising effectiveness is observed both before and after the change. The effect of online advertising is disproportionately high for new products and for products with low awareness in places that have bans. This suggests that online advertising could reduce the effectiveness of attempts to regulate offline advertising channels because online advertising substitutes for (rather than complements) offline advertising.Google (Firm)WPP (Firm