Feds place 150 union pension funds in 'critical' status

The Washington Examiner reports:

The Labor Department says 150 union multi-employer pension funds are in "critical status," meaning that they lack enough assets to meet at least 65 percent of their future obligations.

Another 85 funds are listed as being "endangered," meaning they lack the assets to meet at least 80 percent of their future obligations.

"These are lists of plans whose own funding [levels] puts the plan at risk," said Norman Stein, senior policy adviser to the Pension Rights Center, a nonprofit consumer watchdog group. That status gives the trustees the option of cutting some benefits as part of a rehabilitation plan to get the program back to health. They are not obligated to makes cuts, though, Stein notes.

Isn't every pension plan really a Ponzi scheme? How does any pension plan know how many people will be paying into the fund 10 years from now?