Two economists have come up with a startling and provocative explanation for why countries in colder climates tend to enjoy so much more economic prosperity than countries in tropical areas.
The answer, they say, is Jack Frost.
William Masters of Purdue University and Margaret McMillan of Tufts University used global climate data that has been collected by international organizations since 1960 to conclude that those frosty winter days can do much to determine which countries rise and which fall on the global economic scale.
That answer seems so simple that it almost sounds flippant, but this is serious research, published in the September issue of the Journal of Economic Growth.
"It's very clear in the data," says McMillan. "It's so obvious it just jumps out at you."
Economists have struggled for many years to explain why so much of the world's wealth is concentrated in countries located in temperate rather than tropical regions, and many have suggested that weather must play a part, but this is the first time that economic progress has been linked directly to frost.
"This is the first time that we've had an easy way to compare the climates of different regions in a way that seems to be economically meaningful," Masters says.
Reduced Disease, Better Crops
The economists conclude that frost plays a powerful role in two critical areas. It suppresses diseases such as malaria, and it improves agricultural yields.
The researchers plotted the number of days of frost per month in regions around the entire world. Then they added in the growth in gross domestic product per capita in each region.
"When you do that on a graph, you see there's a positive correlation between the number of frost days and GDP growth," McMillan says.
In other words, if the ground doesn't get cold in the winter, it's going to be a lot tougher to make a living.
"It has been possible for people to become quite civilized and have lots of population growth even in tropical regions," Masters says. "It's just that they've had a hard time getting rich."
All Because of Jack Frost?
Masters says cold weather kills off many disease-carrying germs and insects, thus giving countries in higher latitudes a better chance of keeping deadly killers like yellow fever and malaria under control. That frees up more resources for other purposes, like cultivating crops.
And the crops do better, he adds, because frost enriches the organic material in topsoil.
"In the tropics, that matter is broken down by insects and microbes very quickly, and the nitrogen and carbon in the dead plant material evaporates into the air or is leached into the ground by rainwater," he says. "In a temperate zone, that nitrogen and carbon builds up and remains in the soil in the form of organic matter."
Winter freezing also traps more moisture in the topsoil, preparing the way for spring growth.
The researchers are quick to admit there are exceptions to the frost-produces-riches hypothesis. North Korea and Mongolia are in temperate zones, but both are poor. However, "they have totalitarian governments and exist in isolation," Masters says. Hong Kong and Singapore enjoy great wealth in the tropics, but both are major trading centers.