BOSTON (AP) — Presidents of eight private colleges in the U.S. were paid more than $2 million in 2014, the most ever to hit that mark, according to a new study.

They join a total of 39 chiefs who made more than $1 million that year, passing the previous high of 32 the year before, according to new annual rankings released Sunday by the Chronicle of Higher Education.

Overall, pay across the industry has continued to climb. For presidents of private colleges who worked in 2013 and 2014, average yearly pay rose by 8.6 percent, to $513,000.

Topping the list was Jack Varsalona, president of the 15,000-student Wilmington University, in Delaware, whose salary and benefits totaled $5.4 million.

He was followed by Chancellor Mark Wrighton, of Washington University in St. Louis, who was paid $4.2 million, and President R. Gerald Turner, of Southern Methodist University in Texas, who was paid $3.3 million.

Other private colleges with presidential salaries topping $2 million in the new rankings are the University of Pennsylvania, Columbia University, Northwestern University, Belmont University and the University of Chicago. Previously, the highest number of schools to hit that mark was five, in 2013.

For the three highest paid, most of their earnings came as one-time payments they had previously been promised for reaching certain milestones. Varsalona, for example, received about $4 million for staying on the job until at least age 65. He's now 68.

Often known as "deferred compensation," those types of arrangements have become common at many colleges. Schools say it helps prevent their competitors from poaching strong leaders.

But critics say pay and benefits for university presidents have become excessively lavish, especially at a time when families face rising tuition costs.

Richard Vedder, an economist and director of the Center for College Affordability and Productivity at Ohio University, said the top presidential earnings in 2014 were "obscene" but in line with the industry's upward trend.

"This kind of pay is hardly ever justified in my opinion," Vedder said. "Even the $2 million dollar salaries that some of the Ivy League presidents are getting is way out of line with historic norms."

Varsalona's earnings are the second-highest the Chronicle has ever reported, following a $7.1 million package paid to Shirley Ann Jackson, at Rensselaer Polytechnic Institute in New York, in 2012.

In a statement, Wilmington University said Varsalona's pay reflects his "extraordinary service to the university" and that he wouldn't have received the deferred pay if he had been fired or if the school was struggling financially.

The University of Washington in St. Louis called Wrighton's one-time payment an anomaly and emphasized that his base salary was $943,000 in 2014.

Michael Boone, chairman of the board of trustees at Southern Methodist University, said Turner's payment plan has "served its purpose well" and that he has given "two decades of extraordinary service."

The new rankings listed presidents of private colleges only, who are typically paid more than leaders of public universities. A separate survey by the Chronicle in July found that the chiefs of five public schools topped $1 million in 2015.