More than two decades after the end of military rule, the current turbulence in Ecuador once again raises the question of how stable South America's democracies are.

In political terms, South America seems to be dividing into two.

On the one hand, a group of Andean countries - Venezuela, Colombia, Peru, Ecuador and landlocked Paraguay - continues to display signs of instability.

On the other hand, Brazil, Argentina, Uruguay, Bolivia and Chile are rapidly becoming solid democracies.

In neither case is there any prospect of a return to all-out authoritarian rule, by the military or anybody else.

South America's generals left office, after their last period in power, accused of human rights abuses and chaotic economic mismanagement.

Few of them want to repeat that experience.

Other possible coup leaders - if they came to power - would find their lives made almost impossible by international pressure, especially from the United States.

Unlike some African countries, South America is sufficiently developed to have a big stake in the global economy, so approval from the outside world is crucial.

In addition, the information revolution and the spread of education have given ordinary people a much clearer idea about the benefits of democracy.

But in the unstable half of the continent, the past few years have not exactly been problem-free.

The unstable half

Venezuela experienced two coup attempts in 1992, followed a little later by the forced resignation of the president, Carlos Andres Perez, on corruption charges.

The man who led the first coup attempt, Hugo Chavez, is now president.

Controversy rages about whether he is a visionary leader or an authoritarian populist.

Another leader with authoritarian tendencies is Peru's Alberto Fujimori, who has won two elections by handsome margins.

But in between them, in 1992, he staged a "self-coup", dissolving Congress with the support of the military and having a new constitution written which, among other things, allowed him to stand for re-election for a third term, despite opposition protests.

Paraguay has been through two reasonably clean presidential elections since General Stroessner fell from power in 1989. But its democratic culture is weak.

In March 1999, the country's most popular politician, Lino Oviedo, and his protégé, President Raul Cubas, were forced to flee the country after the assassination of the vice-president, Luis Maria Argana.

And then there is Ecuador, where the quest for political stability has been persistently undermined by economic crisis.

In 1997, President Abdala Bucaram was forced out of office by popular pressure; his next elected successor, Jamil Mahuad, has just suffered the same fate.

The solid democracies

Things are very different in the other half of the continent.

Uruguay and Argentina have suffered no constitutional upheavals since the return to democracy.

Brazil did suffer one, in 1992, when President Fernando Collor de Mello resigned after accusations of massive corruption.

But under the current president, Fernando Henrique Cardoso, Brazil shows signs of democratic maturity.

Chile may not seem like such an obvious example of stability; the controversy over the fate of General Pinochet led to fears of a right-wing backlash.

In fact, the recent elections there showed that the polarisation between left and right has, if anything, diminished.

Economic divisions

The only obvious explanation for this division in South America is economic.

The more stable countries also tend to be the most prosperous.

But that does not explain everything.

Venezuela was until recently one of the riches countries in the region.

Bolivia has managed to sort out its politics while most of its population remains dirt-poor.

What is clear is that while South American democracy remains shaky in places, it's still stronger than at any time in the continent's history.