Los Angeles firefighter Donn Thompson had a busy year in 2017. If his pay stubs are to be believed, he literally never stopped working.

Data obtained by Transparent California, a project of the Nevada Policy Research Institute, show that Thompson pulled down $300,000 in overtime pay during 2017, on top of his $92,000 salary. Over the past four years, Thompson has earned more than $1 million in overtime, according to Transparent California's database. Thompson's ability to work so many hours "boggles the mind," says Robert Fellner, director of research at the institute.

To earn that much in overtime pay, Thompson would have had to work more hours than actually exist in a single year. Either the highly paid firefighter found a way to stretch the space-time continuum or something fishy is going on.

Here's how the math breaks down. Thompson, like all firefighters in Los Angeles, works 2,912 hours every year. With a base salary of $92,000, that comes to an hourly rate of $31.60. That means Thompson would earn overtime pay at a rate of $47.40 per hour—that's one and a half times the base rate. But earning $302,000 at a rate of $47.40 per hour would require working more than 6,370 hours. Add that to the 2,912 hours he worked as a salaried employee, and you get more than 9,280 hours worked, despite the fact that there are only 8,760 hours in a year.

Thompson is probably taking advantage of contract provisions that boost overtime pay above the typical rate, says Fellner, though it's unclear for now how that affects the calculations. (Transparent California is awaiting more payroll data from the fire department.)

Cashing in on the Los Angeles Fire Department's generous overtime rules is nothing new for Thompson, who might very well be the highest paid firefighter in American history. A 1996 Los Angeles Times story highlighted Thompson as a prime example of what the paper called "paycheck generosity" at the department. From 1993 through 1995, the Times found, Thompson made $219,649 in overtime pay. At the time, the department was spending more than $58 million annually on overtime, an amount the paper called "budget-wrenching"; it far surpassed what fire departments in other big cities were paying. The Fire Department of New York, for example, at the time paid about a third as much in overtime.

In 2009, when the Los Angeles Daily News reported that the L.A. fire department's overtime budget had grown by more than 60 percent in a decade, Thompson was once again riding high. He had earned "$173,335 in overtime in addition to his nearly $100,000 base salary while working at Fire Station 19 on Sunset Boulevard in Brentwood," the paper reported, citing 2008 figures.

In 2014, when the San Diego Union-Tribune featured Thompson in a story about runaway overtime costs at California fire departments, he told the paper that he "basically lived at the station" and didn't go home very often.

"The first thing [people] think of is firefighters sitting around at the station, but they're not just handing out free money over here," Thompson said. "I'm working hard."

The Los Angeles Times found quite the opposite when it investigated overtime. In the 1996 article, the Times said most overtime hours are not connected to "fires or other emergencies. Instead, most of it goes for replacing those who are out because of vacations, holidays, injuries, training, illnesses or personal leaves."

While Thompson's payouts are certainly eye-popping, he's hardly the only firefighter in L.A. reaping huge taxpayer-funded earnings. During 2017, the Los Angeles Fire Department had 512 employees who cashed in with at least $100,000 in overtime pay, according to Transparent California. That's a tenfold increase over the 51 employees who got six-figure overtime pay as recently as 2012. Thompson was one of 26 employees to get at least $200,000 in overtime pay last year, when the department reported spending $198 million on overtime pay—a 74 percent increase since 2012.

Perhaps the only silver lining for the taxpayers is the fact that overtime pay can no longer be factored into pension benefits, a consequence of a 2012 pension reform bill signed by Gov. Jerry Brown. It is perhaps not surprising that a dramatic increase in overtime payouts began the same year Brown signed that bill.