By MARY WILLIAMS WALSH and AMY SCHOENFELD
In Yonkers, more than 100 retired police officers and firefighters are collecting pensions greater than their pay when they were working. One of the youngest, Hugo Tassone, retired at 44 with a base pay of about $74,000 a year. His pension is now $101,333 a year.

It’s what the system promised, said Mr. Tassone, now 47, adding that he did nothing wrong by adding lots of overtime to his base pay shortly before retiring. “I don’t understand how the working guy that held up their end of the bargain became the problem,” he said.

Despite a pension investigation by the New York attorney general, an audit concluding that some police officers in the city broke overtime rules to increase their payouts and the mayor’s statements that future pensions should be based on regular pay, not overtime, these practices persist in Yonkers.

The city has even arranged for its police to put in overtime as flagmen on Consolidated Edison construction sites. Though a company is paying the bill, the city is actually reporting the work as city overtime to the New York State pension fund, padding future payouts — an arrangement at odds with the spirit of public employment, if not the law.

The Yonkers experience shows how errors, misunderstandings and wishful thinking are piling hidden new costs onto New York’s public pension system every year, worsening the state’s current fiscal crisis. And the problem is not just in New York. Public pension costs are ballooning everywhere, throwing budgets out of whack and raising the question of whether venerable state pension systems are viable.

In fact, the cost of public pensions has been systemically underestimated nationwide for more than two decades, say some analysts. By these estimates, state and local officials have promised $5 trillion worth of benefits while thinking they were committing taxpayers to roughly half that amount.

The use of public money for outsize retirement pay really stings when budgets don’t balance, teachers are being laid off, furloughs are being planned and everything from poison-control centers to Alzheimer’s day care is being cut, as is happening in New York.

According to pension data collected by The New York Times from the city and state, about 3,700 retired public workers in New York are now getting pensions of more than $100,000 a year, exempt from state and local taxes. The data belie official reports that the average state pension is a modest $18,000, or $38,000 for retired police officers and firefighters. (The average is low, in part, because it includes people who worked in government only part time, or just a few years, as well as surviving spouses getting partial benefits.)

Roughly one of every 250 retired public workers in New York is collecting a six-figure pension, and that group is expected to grow rapidly in coming years, based on the number of highly paid people in the pipeline.

Payouts for Decades

Some will receive the big pensions for decades. Thirteen New York City police officers recently retired at age 40 with pensions above $100,000 a year; nine did so in their 30s. The plan’s public information officer said that the very young retirees had qualified for special disability pensions, which are 50 percent larger than ordinary police pensions. He said several dozen of the highest-paid New York City police retirees had disabilities related to 9/11 and the rest of the disabilities resulted from injuries in the line of duty.

In virtually every case, the officials who granted the rich pensions thought they were offering something affordable, because the cost estimates were too low.

Before Yonkers adopted a richer pension formula for police in 2000, for instance, it was told the maximum cost would be $1.3 million a year. But instead, the yearly cost is now $3.75 million and rising.

David Simpson, a spokesman for the mayor of Yonkers, said pension cost projections were “often lowballs,” so the city could get stuck. “Once you give something, you can’t take it away,” he said.

Police pensions and overtime have been a sore point in Yonkers for many years and were the subject of an exposé in The Journal News in Westchester in 2009. A special audit of police overtime in Yonkers in 2007 found that the police department had failed to enforce its own rules, creating pervasive opportunities for abuse.