In yesterday’s column, Daily News journalist Errol Louis quotes Lillian Roberts, the head of the city’s civilian DC-37 union, saying that “When our people retire, the average one will receive something like $20,000 a year.”

That may be true of current retirees. Data from the city’s largest civilian pension system — its city employees are a good proxy for DC-37 — shows that in 1998, the average salary of an active member was $41,076, working out to a $20,538 annual pension or so.

As of 2006, though, the average active member was earning $56,171, meaning, eventually, a pension of $28,086 in 2006 dollars.

That’s an 11 percent increase, above inflation, of the expected future pension benefit, in eight years.

And if a person in the private sector wanted to assure such an annual benefit for life, without having to worry about investment risk, he or she would have to amass a bank account of $431,751 upon retirement.