But the CIA's number goes too far in the opposite direction and is plainly wrong. Clear evidence that Cuba is poorer than Brazil comes from a recent programme agreed by the governments of the two nations. For all its other problems, Cuba has made proud boasts that it has outstanding public medicine and large numbers of excellent doctors. By contrast, in Brazil the left-wing government of President Dilma Rousseff has been criticised for poor health standards and under-staffed medical services.

So they have done a deal. Brazil pays dollars to Cuba, Cuba sends 5,000 of its doctors to Brazil, and the Rousseff government announces a scheme of Mais Médicos ("more doctors") to beef up state medicine. All of which might seem excellent for everyone concerned, except Brazil's National Doctors Federation (Fenam) has protested that the Cubans are slave labour. The Brazilian government is paying Cuba about $4,000 a month for each doctor, but only a tenth of that is handed over to the doctors themselves. The president of Fenam has said publicly that the scheme amounted to "the biggest labour fraud we have ever seen". Since the Cuban medics are sent to remote and dangerous regions that their Brazilian counterparts avoid at all costs, there can be little doubt that their true pay levels are much less than those of the Brazilians. As medicine is a favoured profession in Cuba, it must also be the case that Cubans in general are much less well-off than Brazilians in PPP terms.

Both the $300-a-year incomes suggested by mechanical conversion at current exchange rates and the CIA's $10,000-a-year PPP number must be rejected. The correct figure in PPP terms is probably somewhere between $2,500 and $5,000 a head, which is a quarter to a half of the Latin American average. As Cuba was the wealthiest country in tropical Latin America in the Fifties, the verdict is inescapable. The Communist take-over was and remains an economic disaster. Two generations have been cheated of material improvements that they would have enjoyed if they had not lived in a nation that became a shuttlecock in the Cold War. Indeed, several rather banal items of evidence suggest that Cuba has gone backwards.

Two favourite themes of Cuba's tourist postcards are the classic American automobiles of the Fifties that are still driven on the roads, and the best examples of colonial architecture. The popularity of both these themes speaks volumes about the pattern of economic development. Let us take first the high number of American cars from the pre-revolution period relative to cars of a later vintage. Obviously, the age of a nation's car population reflects the timing of purchases and owners' willingness to repair rather than replace. In the Fifties so many Cubans had the dollars to buy foreign cars that they were one of the most widely-held consumer durables in private ownership, which fits with the reputation Cuba then had of being particularly affluent compared with other Latin American countries. In fact, privately-owned cars were so common that the Castro regime did not dare to expropriate and redistribute them. They continued to belong to individuals and families, even as businesses and land were being confiscated by the state.

Many of them were lovingly maintained and repaired, and with their 50 or 60-year-old engines they remain in service today. Wall-to-wall gas-guzzling limousines may nowadays be despised by the environmentally-correct citizens of New York, Chicago and Los Angeles, but they are one of Havana's top tourist attractions. A delicious irony is that what was good for General Motors in the Fifties is also good for Communist Cuba and its tourist industry in the 21st century.