How America's $8.6 trillion cities compare to entire nations

By Andre Tartar and Wei Lu

If New York City were a country, its $1.6 trillion economy puts it just ahead of nearby Canada. Los Angeles would rank just behind Mexico next door.

The US is not only the richest nation in the world but also among the most urbanized. Its top 20 metropolitan areas, with 120 million people, represent around half of the entire country's gross domestic product.

While it makes for a playful exercise, it's important not to read too much into these comparisons. For example, the "gross metropolitan product" of the US capital of Washington is in broad terms a match for the GDP of Nigeria and Sweden — two very different countries — and in no way comparable to either, especially by standard of living.

What is interesting is the volume of economic activity these densely packed urban centers are able to generate, so much as to compete, nominally at least to entire nations. Whoever said size doesn't matter never visited an American city.