When I entered the University of Chicago's Ph.D. in Economics in 1988, I believe that my entering class was 50% foreign. Today, I would guess that UCLA's entering class is 20% domestic and I've heard similar numbers for other programs. If fewer young U.S citizens enter Ph.D programs and if U.S born students and foreign students are of equal ability, then we should see a growth in foreigners at the top of new cohort rankings of top economists. I look at the names of the top ranked REPEC research scholars at this website and I think I see a sharp reduction in "U.S names" for the 5 year and 10 year cohorts versus the 20 year cohort. Even for the 20 year cohort, I believe that only 25% of the names are U.S born. I am proud to be #74 in the 20 year cohort and I will point out that my 3 books are even counted in that ranking! Keep in mind that roughly 900 Ph.D. economists are produced each year so there were roughly 18,000 people in this "birth cohort".
So, the 5 year cohort is the set of Ph.D economists who graduated after 2007 , the 10 year cohort is the set of Ph.D economists who graduated after 2002 and the 20 year cohort includes Ph.D. economists who graduated after 1992. These data highlight the globalization of academic economics. Is this bad news for U.S economics? I don't think so but it has implications for which subfields of economics are "hot" such as development.
Here are the UCLA statistics by rank;
Full Professor; 8 of 15 are born in the USA
Associate Prof: 0 of 6 are born in the USA
Assistant Prof: 3 out of 14 are born in the USA
So, that's an example of the regime shift.