In Cuba, it seems time and age might succeed where both the carrot and the stick have failed.
The Americans applied a strict embargo against Cuba when Fidel Castro established a dictatorship in 1959, but it didn't accomplish much more than sending the dictator fleeing into the hands of the Soviet Union and (later) Venezuelan strongman Hugo Chavez.
President Barack Obama offered some modest modifications to the embargo in 2009, but to no effect. Canadians, on the other hand, have traded billions of dollars worth of goods since the 1970s, but the totalitarian state persists.
The Castro regime opened the economy slightly to private enterprise since the collapse of its Soviet sponsor, but the motive was related more to the desperate condition of the economy than a genuine desire for political reform.
When Fidel Castro stepped down several years ago for health reasons, there was hope his brother and successor, Raul, would loosen the state's grip on the lives of the people, but other than a few token gestures, the decadent old system chugged along under the tutelage of equally decrepit leadership.
Now, however, Raul Castro has announced he will step down in five years and he has named a relatively young 52-year-old to replace him.
The Americans have long said the rule of the Castros was an impediment to better relations, but if a new face emerges in Cuban political life, it could be an opportunity for a new dialogue that links trade with political reform.
That assumes, of course, the new leader is interested in ending the failed dictatorship, a Cold War anachronism that might have been well-intentioned 50 years ago, but which never had any legitimacy as a representative of the people.
It is only a matter of time before it embraces reform, or collapses under the weight of its moral and political bankruptcy.