analyzed 167,265 payroll records from 2009 to 2013, provided by the Philadelphia Finance Department.

Our calculations are based on employees working a 37.5-hour week and earning 1.5 times their hourly wage for overtime, both standard policies for unionized city workers.

Our calculations sought to show the minimum number of working hours necessary to accrue the overtime the employees earned. We accounted for two weeks of vacation, and allowed for the possibility that employees worked 7.5-hour days on all 11 city-recognized holidays, when they would have been paid double their hourly rates.

If employees took more vacation time, or worked fewer holidays, they would have had to log even more overtime hours to amass their earned amounts.

We also calculated the effect that overtime earnings would have on the pensions of selected non-police and fire employees. We used the employees' hire dates, provided by the city, to determine which pension plan they would be eligible for. Following example scenarios in city pension plan documents, our pension-plan calculations were based on 25 years of service, unless a worker had already worked more than that amount, in which case we used their current number of years of service.