The old joke about the Human Development Index is that it was designed to show Americans how many countries were better than us. Typically, Scandinavian and Western European countries would fill the top ten, pushing the United States, discouragingly, into the mid-teens. But not this year. On the occasion of HDI's 20th anniversary, the United States finally made the top five.

We are number four! We are number four!

To learn more about the rankings, I spoke with William Orme from the Human Development Report about the survey -- why some nations shot up the rankings, why others fell and, most importantly, what makes America so great all of a sudden.

The Human Development Index was developed to create a more human alternative to GDP. Whereas GDP measures economic output, HDI measures the well-being of its citizens.

The formula is a three-legged stool, supported by the classic triad of health, income and education indicators. This year, researchers and statisticians updated the equation. Health continues to be measured by life expectancy. But with income, they shifted from Gross Domestic Product -- what a country produces -- to Gross National Income, what a country earns, which includes financial aid and remittances from expats to their families. For developing countries this is a big deal. Remittances to Mexico are larger than oil exports. In the Philippines, they are the largest source of foreign exchange.