摘要：Although economists have long been aware of Jensen's inequality, many
econometric applications have neglected an important implication of it: the
standard practice of interpreting the parameters of log-linearized models
estimated by ordinary least squares as elasticities can be highly misleading in
the presence of heteroskedasticity. This paper explains why this problem arises
and proposes an appropriate estimator. Our criticism to conventional practices
and the solution we propose extends to a broad range of economic applications
where the equation under study is log-linearized. We develop the argument using
one particular illustration, the gravity equation for trade, and apply the
proposed technique to provide new estimates of this equation. We find
significant differences between estimates obtained with the proposed estimator
and those obtained with the traditional method. These discrepancies persist even
when the gravity equation takes into account multilateral resistance terms or
fixed effects
