On March 18, the Trump administration announced new sanctions on 19 Russians in response to their alleged interference in the 2016 election campaign. Although largely symbolic – freezing a few assets will hardly bring down the Russian economy – these measures follow a host of sanctions programs against Russia, North Korea and the 18 other countries on the US Treasury Department’s official list. The message is clear: the present era is an era of sanctions. All of which raises the question: do sanctions work? In a classic study, Hufbauer and co-authors approach this question through a systematic study of 174 historic sanctions programs. Overall, they find that sanctions lead to “success” – in the sense that they induce the desired change in behavior – in around a third of all cases. Not great, you might say, but not bad either.However, this number looks less impressive once one realizes that sanctions are almost always used in combination with a battery of other foreign policy measures like diplomacy and the threat of war. In the absence of further investigation, one cannot know whether it was sanctions or these other measures that led to the desired outcome. Hence the one-third figure is best viewed as an upper bound on the efficacy of sanctions.Indeed, if one restricts attention to cases in which sanctions alone were employed, one finds scarcely any successes – perhaps as few as five. And many of these successes are fairly trivial. For instance, the threat of Arab League sanctions induced Canada to abandon its plan to move its embassy from Tel Aviv to Jerusalem in 1979. Furthermore, it is rather unclear through which mechanism sanctions are supposed to change their target’s behavior. One idea is that the pain of sanctions will encourage populations to revolt against their governments. But it seems just as plausible that sanctions will be blamed not on the targeted governments but on the author nations, generating a nationalistic counter-reaction and shoring up domestic support. As Mussolini put it in 1935: “To sanctions we will reply with our discipline, with our sobriety and with our spirit of sacrifice.”Another idea is that sanctions will weaken their target militarily through economic damage. However, while governments may respond to falling GDP by cutting military spending, they could also raise taxes, borrow more or cut spending elsewhere. In addition, even if sanctions do succeed weakening their target’s military, this need not induce any concessions in an era in which even small militaries can inflict incalculable suffering on civilian populations.Sanctions can also provide governments with convenient excuses for domestic woes, as the case of Cuba illustrates. While decades of sanctions have failed to topple the Castro regime, they have given them the perfect excuse for Cuba’s poor macroeconomic performance – something which might other - wise be laid at the door of its inefficient economic system. In addition, they have allowed Cuba to paint itself as the spirited underdog in the fight against American imperialism.Finally, one must remember that even if sanctions do “work” in the sense of achieving the goals of their authors, they may not “work” for their targeted populations, many of whom may be killed by the combination of rising food prices and economic collapse. In Iraq, for example, sanctions are estimated to have led to the deaths of hundreds of thousands of children, although the exact number remains contested. Even if these sanctions had led to their desired outcome – and they did not – they would have constituted an indefensible foreign policy. In response to episodes such as these, the focus has shifted to the kind of sanctions just extended by the Trump administration which target key individuals and organizations rather than wider populations. But what these measures gain in humanitarianism they lose in efficacy. Senior Russian figures dismiss them entirely. “The only things that interest me in the US are Tupac Shakur, Allen Ginsberg and Jackson Pollock,” said Putin aide Vladislav Surkov. “I don’t need a visa to access their work.” The current round of sanctions may be good politics for Trump, but whether they will change Russian behavior is more doubtful.The author is a graduate student in economics at Oxford University.