A Mexican migrant to the U.S. is five times more productive than one who stays home. Why is that? The answer is not the obvious one: This country has more machinery or tools or natural resources. Instead, according to some remarkable but largely ignored research—by the World Bank, of all places—it is because the average American has access to over $418,000 in intangible wealth, while the stay-at-home Mexican's intangible wealth is just $34,000.

But what is intangible wealth, and how on earth is it measured?

...the World Bank finds, "Human capital and the value of institutions (as measured by rule of law) constitute the largest share of wealth in virtually all countries." According to their regression analyses, for example, the rule of law explains 57 percent of countries' intangible capital. Education accounts for 36 percent.

Average per capita wealth in OECD countries is $440,000, consisting of $10,000 in natural capital, $76,000 in produced capital, and a whopping $354,000 in intangible capital. (Switzerland has the highest per capita wealth, at $648,000. The U.S. is fourth at $513,000.)

By comparison, total wealth for the low income countries averages $7,216 per person consisting of $2,075 in natural capital, $1,150 in produced capital and $3,991 in intangible capital. The countries with the lowest per capita wealth are Ethiopia ($1,965), Nigeria ($2,748), and Burundi ($2,859). In fact, some countries are so badly run, that they actually have negative intangible capital. Through rampant corruption and failing school systems, Nigeria and the Democratic Republic of the Congo are destroying their intangible capital and ensuring that their people will be poorer in the future.