Notwithstanding those exceptions, "if you look around the world, you can see that most of the poor countries are in the tropics. The exceptions have been able to get out of this low-level productivity trap by opening up to trade and not relying heavily on agriculture," McMillan adds.
Agriculture Has Always Been Key
If what the economists are saying holds up to further scrutiny, it really means that humans haven't changed much since the beginning of civilization. In his book, Guns, Germs, and Steel, Jared Diamond makes it clear that the road to civilization began when humans first learned that they could grow crops and domesticate animals instead of hunting and gathering.
Agriculture forced humans to settle down in villages, instead of roaming the land in search of food, and it freed up some members of the clan for other pursuits. Some were then able to become kings, bureaucrats, warriors, scientists and artists.
Diamond, professor of physiology at the UCLA School of Medicine, argues that without agriculture, humans would never have had the time to shape the first instruments of war out of metal, nor would they have domesticated horses to carry them off to battle, nor would they have developed the implements of industry that brought us to where we are today.
So during that long journey those who were successful at farming became rich and powerful, conquering much of the world. One might think that disparity between the haves and the have-nots would subside over thousands of years, but it hasn't.
"What we are finding is a 1 or 2 percent per year difference in growth rate," Masters says. "So year by year, a society with frost seems to grow 1 or 2 percent faster."
The research by the two economists is too recent to have provoked much comment from other disciplines, but the reaction so far is mixed.
"There's been a lot of interest," Masters says, "but many people are violently allergic to any explanation that has a whiff of geographic determinism.
"People are very strongly invested in the idea that a country can pull up its socks, as the British say, get its act together, and get the right institutions like the ones that we believe helped make us rich, and that's the road to riches.
"Institutional factors do matter hugely," he adds, but in the end, old Jack Frost is still going to have a say in who gets rich, and who stays poor.