Econometrics
Paper Session
Saturday, Jan. 4, 2025 2:30 PM - 4:30 PM (PST)
- Chair: Andrew Foerster, Federal Reserve Bank of San Francisco
Testing for Instrument Validity with Higher-Order Cumulants
Abstract
Instrumental variables estimators are commonly used in economics and finance toestablish causal relationships. Although instruments that fail the exclusion restriction
do not reliably estimate parameters of interest, testing the exclusion restriction is
uncommon, due to the difficulty of finding multiple valid instruments. We derive
closed-form instrumental variable estimators that allow for tests of over-identifying
restrictions even for the case of a single valid instrument. We also derive estimators
that are consistent when instruments and regressors are mis-measured with correlated
errors. Monte Carlo simulations suggest that our estimators have power to reject even
in relatively small samples. We also apply our estimators to the IV regressions of Mian
and Sufi (2014) and cannot reject the null hypothesis that the exclusion restriction
holds.
Trimmed Mean Group Estimation of Average Treatment E ects in Ultra Short T Panels under Correlated Heterogeneity
Abstract
Under correlated heterogeneity, the commonly used two-way fixed effects estimatoris biased and can lead to misleading inference. This paper proposes a new trimmed mean
group (TMG) estimator which is consistent at the irregular rate of n^{1/3} even if the time
dimension of the panel is as small as the number of its regressors. Extensions to panels
with time effects are provided, and a Hausman-type test of correlated heterogeneity
is proposed. Small sample properties of the TMG estimator (with and without time
effects) are investigated by Monte Carlo experiments and shown to be satisfactory and
perform better than other trimmed estimators proposed in the literature. The proposed
test of correlated heterogeneity is also shown to have the correct size and satisfactory
power. The utility of the TMG approach is illustrated with an empirical application.
JEL Classifications
- C0 - General