SPost13 relies heavily on Stata's margins command which was introduced in Stata 11. The commands were written to take advantage of features introduced in Stata 13, so some features (e.g., tests of average discrete changes of some types) will not work in Stata 11 or Stata 12. We cannot support problems encountered with Stata 11. If you are using Stata 11 or 12 and want to run our sample do-files, use the package spost13_do12, not spost13_do. 01Sep2014