[cameldrv]

One thing is that getting a PhD is a good way to get into the U.S. As a foreigner, many visa and job opportunities open up to you with the PhD.

For an American, it's less of a good deal. Once you have the PhD, you make somewhat more money, but you're trading that for 6 years of hard work and very low pay. The numbers aren't favorable -- you have to love the topic for it to make any sense.

As a result, U.S. PhD programs are heavily foreign born.

[sharadov]

A PHD is a faster path to a green card as well - especially for people born in China and India where the green card backlog is decades long.