The number of doctorates awarded by US universities rose 3.4 per cent last year, the biggest one-year increase since 1992, according to an annual survey by the Nat­ional Science Foundation.

The increase marks the second consecutive year that more doctorates were awarded, with international students accounting for a growing share of degrees. Of the 42,155 new doctoral recipients in 2004, more than 29 per cent were non-US citizens holding temporary visas - a rise of 18 per cent since 1974. The number of US citizens earning doctorates was down slightly over the past decade.