Why sanctions don't work — but could if done right

US sanctions against Iran, Russia, Afghanistan, China and Venezuela have all made the news in recent weeks. That may seem like a lot of countries that the US is sanctioning. But they're just five of the roughly 23 countries that the US is currently sanctioning around the world.

The Office of Foreign Assets Controls (OFAC) at the US Treasury says sanctions use trade restrictions and the blocking of assets to accomplish foreign policy and national security goals. Some of these sanctions date back to 1996. So how successful have they been?

Not very, says Agathe Demarais, in her new book Backfire: How Sanctions Reshape the World Against US Interests.

Demarais works at the Economist Intelligence Unit, as its global forecasting director. Previously, she worked on sanctions for the French government, as a senior policy advisor to the Treasury. She says a review of all US sanctions since 1970 shows that targeted countries altered their behavior in a way that the US hoped they would just 13 percent of the time.

"The reality is that sanctions are sometimes effective, but most often not, and it is hard to accurately predict when they will work," she says.

From the Cudgel to the Laser

Sanctions have been around in some form or another since the days of Ancient Greece. The French used them (unsuccessfully) during the