William Buiter, chief economist at Citigroup, predicts the US will be the third biggest economy at mid-century. But China will not be number one. That honor goes to India.

How is this all related to 3G?

Buiter has constructed a “3G index” to measure economic progress; 3G stands for “Global Growth Generators” and is a weighted average of six growth drivers that the Citigroup economists consider important:

A measure of domestic saving/ investment
A measure of demographic prospects
A measure of health
A measure of education
A measure of the quality of institutions and policies
A measure of trade openness

Using that index the nations to watch over the coming years are Bangladesh, China, Egypt, India, Indonesia, Iraq, Mongolia, Nigeria, the Philippines, Sri Lanka and Vietnam