GDP per land area.

I knew about the GDP (gross domestic product), a metric for how well an economy is doing. Mostly, GDP is measured per capita, or in other words, per citizen. So China has a lot of money, but seems poor because it also has a lot of people who need to share that money. It's a few bucks per citizen. There is however, also another metric, one that maybe is even more useful for comparison. The GDP per…