A Ministry of Education study says limited opportunities for PhD graduates in New Zealand could be encouraging the country's most skilled to go overseas.
The study looked at whether PhD graduates got jobs in New Zealand after university.
It found that 65% of PhD graduates were working four years after finishing their study, compared with 72% of Masters' graduates and 75% of Bachelor degree graduates.
Author Warren Smart says PhD graduates are more likely to go overseas because of limited graduate opportunities in New Zealand.
Dr Smart says rates of employment for PhD graduates in New Zealand are lower than in Canada and the United Kingdom.