We have worked hard to make the SPost13 commands accurate with most of the serious computation being done by Stata's margins command. We use the commands in our own work and have tested the commands extensively. But, as with all software, there could be errors in the code. If you find a problem, please let us know and we will do our best to correct it. Please check here for details on what we need to know to help you. As with all data analysis, work carefully and use methods that you understand. --Scott Long