no code implementations • 25 Apr 2024 • Jinyong Hahn, Guido Kuersteiner, Andres Santos, Wavid Willigrod
We further show that homogeneous effect models in short panels, and their corresponding overidentification tests, are of central importance by establishing that: (i) In heterogenous effects models, interpreting TSLS as a positively weighted average of treatment effects can impose implausible assumptions on the distribution of the data; and (ii) Alternative identifying strategies relying on long panels can prove uninformative in short panel applications.
no code implementations • 8 Oct 2023 • Manu Navjeevan, Rodrigo Pinto, Andres Santos
This paper develops a class of potential outcomes models characterized by three main features: (i) Unobserved heterogeneity can be represented by a vector of potential outcomes and a type describing the manner in which an instrument determines the choice of treatment; (ii) The availability of an instrumental variable that is conditionally independent of unobserved heterogeneity; and (iii) The imposition of convex restrictions on the distribution of unobserved heterogeneity.
no code implementations • 18 Mar 2023 • Denis Chetverikov, Jinyong Hahn, Zhipeng Liao, Andres Santos
In particular, when the regressor of interest is independent not only of other regressors but also of the error term, the textbook homoskedastic variance formula is valid even if the error term and auxiliary regressors exhibit a general dependence structure.
no code implementations • 18 Sep 2020 • Zheng Fang, Andres Santos, Azeem M. Shaikh, Alexander Torgovitsky
This paper considers the problem of testing whether there exists a non-negative solution to a possibly under-determined system of linear equations with known coefficients.
1 code implementation • 2 Apr 2014 • Oscar Esteban, Gert Wollny, Subrahmanyam Gorthi, Maria-J. Ledesma-Carbayo, Jean-Philippe Thiran, Andres Santos, Meritxell Bach-Cuadra
MBIS supports multi-channel bias field correction based on a B-spline model.