YESTERDAY Cubans celebrated the 81st birthday of their president, Fidel Castro. Although he has not appeared in public since a stomach operation a year ago, Mr Castro is still nominally in charge of the communist country he has led since a revolution in 1959. This makes him the world's longest-serving living leader. Indeed, many rulers coming to power through a revolution or coup, like absolute monarchs, are likely to enjoy a lengthy stint in charge. A few, such as Robert Mugabe, were legitimately elected at some point. Now, however, most rulers use fraudulent democratic elections as a figleaf for their continued reign.