May 18 (Bloomberg) — The number of presidents at public universities making more than $1 million a year more than doubled to nine in the 2012-2013 school year as performance bonuses drove pay higher, according to the Chronicle of Higher Education.

Public college presidents made on average $478,896 last year, up 5 percent from the year before, the publication found in a survey released today. Base salaries rose 1 percent to $403,496. The gain in compensation comes as states have repeatedly cut aid, forcing universities to raise tuition and count more on fundraising, while requiring increased performance standards such as graduation rates to get funding.

"The job is a lot more complicated and the expectations are higher," said Lyn Harper, a senior consultant at Yaffe & Co., a nonprofit health care and higher education compensation adviser in Towson, Maryland. "People are expecting more than they did 10 years ago and these campuses are very complicated."