As a general matter, unilateral sanctions rarely achieve U.S. foreign policy goals. The Peterson Institute for International Economics has concluded that unilateral U.S. sanctions in place from 1970-2000 were effective only 19 percent of the time, and most successes came where a modest policy change – like release of a political prisoner – was sought. Moreover, sanctions may make the problems they are intended to address worse by providing an excuse for the targeted government to blame its failures on outside pressures and to rally support for its regime.