There are a couple of reasons the pension funds that pay retired teachers, police, elected officials, and other public servants have become more expensive for taxpayers - eating up $1 of every $6 in Philadelphia's city budget, for example.

It's easy to blame the exotic, sometimes politically connected, investments in unprofitable projects and secretive far-off funds that the pensions' trustees - many of them political appointments - have too often approved.

But it's probably more costly that politicians years ago fattened pension benefits but didn't set aside enough money to pay for them along the way. And they still don't.

Especially in New Jersey and Pennsylvania. Moody's Investors Service says in a new report New Jersey kicked in just 28 cents for every dollar needed to balance spending liabilities with income in 2013.

That's the lowest contribution any state made toward the "actuarially determined" target for a pension system to keep up with expenses that aren't covered by investment profits or workers' pension contributions, according to Moody's.

Years of underpayment mean the assets set aside to pay current and future New Jersey retirees now trail the estimated costs by $42 billion, according to a report prepared for Gov. Christie's Treasury Department in September.

The shortfall is double what it was in 2007; it has grown worse by $6 billion over the last two years, despite the bull market in U.S. stocks.

Pennsylvania, whose pension assets are also many billions below liabilities, spent just 42 cents for every dollar it needed to keep its own pension deficit in check in 2013, Moody's reported.

Only New Jersey and Virginia were stingier. By contrast, more than two-thirds of the states put in at least 90 cents for every dollar needed to keep up with all the checks flying out the door. They pay now so they don't have to pay a lot more later.

It's easier to focus on investments. Pennsylvania Auditor General Eugene DePasquale went to Norristown last week to praise Montgomery County's new approach.

Montco last year streamlined its investments by firing high-fee "alternative" buyout fund managers and "active" stock-pickers, in favor of cheaper Vanguard and SEI index funds.

At first glance, Montgomery County's approach looks pretty efficient: The county says its low-fee investments returned 16.2 percent after expenses.

The Pennsylvania State Employees' Retirement System, by contrast, with its vast portfolio of buyout, commodity, real estate, and hedge funds, and hundreds of millions in fees to private managers, managed a return of only 15.6 percent. The larger Public School Employees' Retirement System returned 14.9 percent.

But it's early to declare victory. A look at county records shows Montco's pension assets aren't completely all that different from the state's. Montco has about 55 percent of its assets in publicly traded U.S. and foreign stocks; Pennsylvania has 36 percent.

The county is still divesting its buyout funds, which may yet do better than stocks in a bad year - or at least lose less, as they did in the 2008 market collapse.

Look a little deeper, and it turns out Montgomery County isn't doing better than Pennsylvania at making up the payments needed to keep its pensions solvent for the long term.

The county plans to contribute $3.5 million to the fund in 2015. That's better than the zero the county spent in five years under its previous Republican majority.

But it's still just about one-third of the $10 million that its actuaries say Montco would have to pay yearly, and to keep paying, if it doesn't want its plan to eventually become as underfunded as Pennsylvania's or New Jersey's.

Correction: The original version of this column wrongly referenced hedge funds in the county portfolio. Also it misstated the percentage of county investment in U.S. and foreign stocks; it is 55 percent.

215-854-5194 @PhillyJoeD