ADH                     Dataset from Autor, Dorn and Hanson (2013)
ivreg_ss                Inference in an IV regression with a
                        shift-share instrument
ivreg_ss.fit            Inference in an IV regression with a
                        shift-share instrument
reg_ss                  Inference in linear regression with a
                        shift-share regressor
reg_ss.fit              Inference in a shift-share regression
