St. Louis isn’t the only Midwestern city dealing with a pension-fund shortfall. Springfield, Ill., residents face an eventual property-tax increase to pay for police and firefighter pensions, the State Journal-Register reports today.

In part, this sounds like a problem of unfunded mandates:

(Mayor Tim) Davlin blames the legislature, which has boosted — while not providing the money — firefighter pension and death benefits four times since 1999. The council has no control over the pension benefits given to cops and firefighters, but local governments must provide the annual payment from property tax revenue.

But market disappointments also contributed to the problem:

Davlin said Tuesday the rate-of-return estimates have been consistently off in the last 14 years. Since 1994, actuaries have estimated each year that the rate of return on the city’s investments would be 8 percent … In the last 10 years, the fire pension’s actual average rate of return was 5.3 percent. For the police, it was 6.3 percent.

Those figures may sound low, but they’re actually representative of what’s gone on in markets over the past decade.  The Vanguard 500 Index Fund’s 10-year annualized return was 6.0 percent as of Nov. 30.