Using a set of pretty charts, NYT columnist Thomas Friedman put forth in 2006 the First Law of Petropolitics which states "that the price of oil and the pace of freedom always move in opposite directions."

I've reproduced some of the chart below from the May/June 2006 issue of Foreign Policy:

Although convincing, the charts are pretty misleading (see here and here for why that's the case). Still, recent academic research supports the idea that countries reliant on abundant natural resources have a higher chance of being ruled by authoritarian regimes.

And that view has become the conventional wisdom, especially with the help of Oxford economist Paul Collier's book, "The Bottom Billion: Why Poor Countries Are Failing and What Can Be Done About It." Collier's main claim is that one of the most significant causes of war in the developing world is this Resource Curse.

But two other lines of more recent work are raising doubts that there is a consistent link between resource dependence and oppressive rule. A small group of economists argue that natural resource wealth can actually promote democracy. This paper, for example, finds that when oil companies are privately owned, petrol exerts a positive impact on democracy.

And a third faction makes the point that natural resources have no effect on whether a country will develop democratic institutions or not.

Which of these three views is closest to the truth? Stanford's Stephen Haber and Victor Menaldo try to find this out.

A central problem with most of the research, they argue, is the reliance on comparing different countries across a small time period, typically between the 1970s and 2000. By then, most of these nations had already become resource dependent, so it's not easy to tell if it was the resources or some other factor (such as geography, culture, or history) which helped oppressive regimes prevail. (The statistical methods used are also called into question, but that's too technical to get into here, so read the paper if you're interested.)

To get around this, Haber and Menaldo took a longer view. They first investigated what happens to independent nations before and after their economies became resource dependent. They were able identify 10 countries which fit that bill: Mexico, Venezuela, Ecuador, Chile, Norway, Nigeria, Iran, Syria, Algeria, Yemen, Oman, Iraq, and Libya. These are all oil-rich countries except for Chile which is the world's largest copper exporter.

They found no evidence that a growing reliance of government coffers on commodity wealth undermines democracies (through a measure called Polity Score). In other words, countries that were politically free more or less stayed that way after finding natural resources (and countries that were authoritarian before commodity discoveries remained authoritarian).

But it could be the case that resource wealth was a roadblock in the transition from authoritarianism to democracy. So, Haber and Menaldo next looked at what happened to resource-poor countries in the same region as the resource-rich country. If the level of freedom in a country like Iran, Chile, or Nigeria moved differently, and negatively, than other countries in the region they belonged to, then oil and mineral wealth could be a democracy stopper. But that didn't turn out to be the case either.

One last effect of resource wealth could be that it slows the pace of democratic transformation. For example, Chile and Mexico became democracies after discovering copper and oil, respectively. Could they have been even more politically free had they not?

This time, B and C found countries that had similar societies, economies and political institutions as the resource-rich nations right before commodity discoveries were made. They matched Venezuela with Colombia, Ecuador with Peru, Mexico with Brazil, Nigeria with Tanzania, and Chile with Argentina. Did political freedom between each paired country diverge after natural resources were found? Again, Haber and Menaldo found no evidence that this was the case. (In fact, some resource-rich countries became more democratic than their pairs.)

While the findings don't mean that in individual cases a despotic ruler doesn't successfully use resource wealth to his advantage, it strongly suggests there is no such thing as an all encompassing Law of Petro-(or some other commodity)-politics.