The American economy hit an encouraging milestone last month: The private sector has finally regained all of the jobs it lost during the Great Recession, according to the U.S. Labor Department.

So why did the Democratic Senate, by a 59-38 vote that included six Republicans (but neither South Carolina member), pass another extension of unemployment benefits Monday?

Sen. Jeff Merkley, D-Ore., offered this justification for the five-month, retroactive measure: "What we're doing is we're stabilizing families, and we're stabilizing communities."

Actually, this sadly familiar pattern has ritualized the ongoing transformation of unemployment assistance from stopgap help for Americans between jobs to perpetual payments to the long-term jobless.

When the national unemployment rate soared in the wake of the 2008 financial-sector meltdown, peaking at 10 percent in October 2009, there was a strong case for extending those benefits.

However, the jobless rate has fallen considerably since then, and held steady at 6.7 percent in March.

Yet there remains a painful ring of truth to the term "jobless recovery." Millions of the chronically unemployed have given up on finding work and thus are not factored into the formula that produces a misleadingly low official unemployment rate.

So there also remains a politically potent argument for again extending unemployment benefits - especially in this election year.

But that feeds this other grim economic reality: Though the national labor-participation rate (percentage of working-age Americans who have a job or are looking for work) rose slightly to 63.2 percent in March, that's still barely above its lowest point in 3 decades.

And with an aging population inevitably putting an ever-heavier load on Medicare and Social Security, that historic decline in the level of working-age Americans on the job - and paying taxes - exacerbates our nation's long-term fiscal challenges.

That includes the ominous puzzle of who will pay the mammoth price for the unaffordable Patient Protection and Affordable Care Act.

Meanwhile, another extension of jobless benefits might create costly problems - and massive waste - across the land.

As The Washington Post reported Tuesday: "State officials are warning that the bipartisan bill to reinstate federal benefits for the long-term unemployed that passed the Senate on Monday could be a logistical nightmare to implement and could expose the government to extensive fraud."

Their concern stems from the fact that "officials may have no way to certify whether an unemployed person continued to look for work to determine if they are eligible for retroactive benefits."

That doesn't mean the Republican House won't again move to extend benefits, too - though Speaker John Boehner is demanding some compromises rightly aimed at removing federal obstacles, including excessive regulations, to "job creation."

But beyond such political machinations lie these vexing questions for federal lawmakers on both sides of the aisle:

When did the concept of jobless benefits transform from a temporary hand up to a permanent handout?

And if nearly two-fifths of working-age Americans are no longer in the labor force, who will cover the escalating tab for our nation's increasingly endangered entitlement programs?