That's interesting, but (at least from a quick look and a few text searches) they don't seem to explain what their "sanction contribution score" is. How are they sure that the cases where they "worked" are not regression to the mean (some authoritarian regimes just fall from time to time)? And how are they sure that there is not an equal number of cases where they do the opposite of what they intend? (maybe the Castrist regime would have fallen already if the country had been allowed to develop without sanctions).

I am citing here from the conclusions of that book (better, have a look yourself):

Overall, we found sanctions to be at least partially successful in 34 percent of the cases that we documented.

By our standards, successful cases are those with an overall success score of 9 or higher. We emphasize that a score of 9 does not mean that economic sanctions achieved a foreign policy triumph. It means only that sanctions made a modest contribution to a goal that was partly realized, often at some political cost to the sender country.

Yet in many cases, it is fair to say that sanctions were a necessary component of the overall campaign that focused primarily on the projection of military force.

Second, we classify some sanctions as failing to produce a real change in the target’s behavior when their primary if unstated purpose—namely, demonstrating resolve at home, signaling disapproval abroad, or simple punishment—may have been fully realized.