There is a widespread belief among economists that adding additional variables to a regression model causes higher standard errors. This note shows that, in general, this belief is unfounded and that the impact of adding variables on coefficients' standard errors is unclear. The concept of...

There is a widespread belief among economists that adding additional variables to a regression model causes higher standard errors. This note shows that, in general, this belief is unfounded and that the impact of adding variables on coefficients’ standard errors is unclear. The concept of...

In this article, we identify and illustrate some shortcomings of the poisson command in Stata. Specifically, we point out that the command fails to check for the existence of the estimates, and we show that it is very sensitive to numerical problems. While these are serious problems that may...