[from]

"Terrorism, regime destabilization, and policy change related objectives are by far more often assessed as failed, as compared to the other policy objectives. Overall, the average success rate [of sanctions] of around 34% across different policy objectives is very much in line with the effectiveness rate of 34% that is reported in the analysis of Hufbauer et al. (2007) and falls in the middle of the success rates ranging between 27% and 37% form Threat and Imposition of Economic Sanctions (TIES) database of Morgan et al. (2014)."

The paper also notes that "the success rate of sanctions has gone up until 1995 and fallen since then."

http://www.pages.drexel.edu/~cas86/GSDB_FKSYY.pdf

20-35% success rate of sanctions has been replicated a bunch of times. Sanctions are the foreign policy experts form of collective punishment. It seems they largely exist to satisfy the bureaucrat's need to "do something."