When the University of Illinois gave a large pay raise to its longtime athletic director a decade ago, it offered an example of the ever-increasing salary arms race to lure and keep college coaches and administrators.

That raise for Ron Guenther has also quietly become an example of just how much the arms race can cost the state’s struggling pension funds years down the road, as Guenther’s annual university pension approaches $500,000 a year.

It’s part of a broader debate about just how much state taxpayers should subsidize public pensions, including the small set of retirees paid significant sums to oversee or coach college sports teams. That debate is now intensifying at the state’s flagship university, with research from a professor at the campus.

U. of I. professor Jay Rosenstein is a documentary filmmaker best known for a 1997 film criticizing the use of Native American mascots for sports teams, including at U. of I. His latest project has focused on the cost of college athletics, and as part of that he spent five years looking into the salaries and pensions of U. of I. coaches and administrators.

Rosenstein used a mix of records obtained through the state’s open records act and other information gathered by the Better Government Association advocacy group to conduct an investigation he’s called “The Multi Million Dollar Head Fake.” The findings are published on his website, theheadfake.org, and at HuffPost.

He argues the salary arms race was sold to taxpayers as a win-win: that the university could pay big bucks to keep and lure talented people, who in turn could produce a program that would bring in more than enough money to cover those higher salaries.

Instead, he said, the university and its students subsidize the program, and taxpayers contribute to large pension tabs years later. He tabulated the cost of retirement checks for 18 former U. of I. coaches and sports administrators at more than $2.6 million a year — with Guenther topping that list.

“You see a coach get another $200,000 or $300,000 raise, and people would say, ‘Well, it’s ridiculous, but they (the athletic department officials) are paying out of their own money and I guess it’s OK.’ Now you see, when they give a raise like that, they were handing the taxpayers a bill.”

The university’s athletic department said it’s not that simple.

Department spokesman Kent Brown said that of the top 500 paid state retirees, only three come from the university’s athletic department: Guenther and former basketball coaches Lou Henson and Jimmy Collins. Henson’s annual pension is $347,058 and Collins’ is $200,015, the university said.

For more recently hired coaches and administrators, state law limits how much pay can count toward state pensions.

Illinois football coach Lovie Smith, for example, has a six-year, $21 million contract. His pension is calculated based on a salary of only $270,000, not the more than $3 million he averages in earnings per year, according to his contract. And there are other rules on how long he has to work, and how old he has to be, to start collecting a traditional state retirement check.

And, in recent years, any public agency giving unusually high pay raises must send additional money to a pension fund to cover the expected pension boost from the raise. U. of I.’s athletic department has had to do that at times.

But that still may not be enough to cover the added expense when a public agency grants large pay raises at the end of a career — a practice critics deride as pension-spiking.

During Guenther’s 19-year tenure, the Elmhurst native was credited with modernizing the university’s athletics program and facilities, partly through aggressive fundraising, even if the university struggled to show sustained success on the football field.

As the athletics budget increased, so did Guenther’s pay, from $120,000 in 1992 to $410,000 by mid-2005, U. of I. data show.

Then, in July 2006, came his biggest raise yet: $90,000, to take him to $500,000 a year. It was defended as a much-needed raise to keep Guenther in line with his peers.

The campus newspaper, The Daily Illini, called the salary increase “eye-popping” in an editorial at the time but opined it was fair because the athletic department “is a self-sufficient entity, receiving money from donors and revenue, not the University nor the state.”

That pay increase would help set the stage for a more lucrative pension subsidized by taxpayers.

Pensions for state employees of that era are based on the worker’s highest four years of pay, typically the last four. In Guenther’s case, he continued to get raises and a bonus, and his last four years’ salary averaged more than $600,000 a year before he retired in July 2011, the State Universities Retirement System, known as SURS, told the Tribune.

He also had spent a long time as a public worker: nearly 32 years, plus credit for an extra year for unused sick time, SURS records show. Under the pension formula, Guenther qualified for just over 72 percent of his average salary.

That pension also grows at 3 percent a year, records show. So that’s how Guenther, 72 years old and seven years into retirement, is now being paid a pension of $473,094 a year from SURS. It is set to top $500,000 a year in 2019, based on a Tribune analysis of SURS’ retirement formula.

Some of Guenther’s pension was fronted by Guenther from paycheck deductions he made over the years. SURS did not immediately say how much, but records it provided to Rosenstein show the figure at $615,000 including interest.

The university athletic department also contributed about $100,000 as part of a law that forces public agencies to pay some of the pension costs of unusually high raises.

Still, those contributions from Guenther and the athletic department are not enough to cover even two years’ worth of Guenther’s pension.

The rest comes from taxpayers, and it adds to the weight of a state pension system that is among the worst-funded in the country from years of big promises to state employees matched with little savings by state lawmakers.

SURS’ assets, for example, could be expected to meet just 43 percent of the pension promises made to current and past employees, according to a 2016 review of the state pension funds. SURS did not respond to a request for an interview.

Messages for Guenther left with the university and a current employer were not returned.

Guenther is allowed to earn as much as $300,000 a year while still keeping his pension, according to state records.

After retiring from U. of I., he became a consultant for the Big Ten Conference. The conference declined to say how much he’s paid.