In its latest rankings of the "top 1,500" law professors worldwide---that is, both those in the United States and those teaching in other countries---Professor Camp placed 266th in recent (i.e. past 12 months) downloads. That placed Camp at 16th among all tax professors. For a table of the top 25 tax profs, see http://taxprof.typepad.com/taxprof_blog/  There are current over 220,000 authors who have posted articles and papers on SSRN.