The Question
Over the last 25 years what has been the academic preparation for winners of
Nobel Laureates Prize in Economics? Such as economics, mathematics,
finance, etc.
The Answer
Almost all of the winners have had Ph.D.'s in economics, with a few exceptions.
You can get a more complete picture by going to the Nobel Prize page and
clicking on the "other resources" links to each winner -- which generally takes
you to the person's homepage, where you'll find c.v.'s, listings of degrees, etc.
I've found these exceptions, but there may be more:
2003 Clive W.J. Granger
Granger's Ph.D. is in Statistics
2002 Daniel Kahneman
Kahneman's Ph.D. is in Psychology
1994 John C. Harsanyi, John F. Nash Jr., Reinhard Selten
Harsanyi's Ph.D. -- Philosophy and later Economics;
Nash's Ph.D. -- Mathematics;
Selten's Ph.D. -- Mathematics
1978 Herbert A. Simon
Ph.D. in Political Science