ivmodel: An R Package for Inference and Sensitivity Analysis of Instrumental Variables Models with One Endogenous Variable

We present a unified R software ivmodel for analyzing instrumental variables with one endogenous variable. The package implements a general class of estimators, k-class estimators, and two confidence intervals that are fully robust to weak instruments. The package also provides power formulas. Finally, the package contains methods for sensitivity analysis to examine the sensitivity to the the instrumental variables assumptions. We demonstrate the software on the data set from Card (1995), looking at the causal effect of levels of education on log earnings where the instrument is the proximity to a four-year college.