James Pethokoukis from AEI always tweets on NFP day what the unemployment rate would be if the participation rate was the same as when Obama came into office. I think he said last week that it would be 10.3%. Of course the participation rate has been declining for 15+ years so it's not a new phenomenon.
However, it's not the "only reason" as the number of working people is up since the low (129.3 million in February 2010) by some 6.2 million (135.5 million in April 2013). We are still 2.6 million away from the peak of 138.1 million in January 2008.
Of course, the population has grown in that same time period, so the number of “new” jobs has to be compared to the number of new jobs required just to employ the new workforce.
QE isn’t sustainable, so what is the end game?
Well, more like almost 13 years but who's counting.
Leftists like to blame the decline in 2009 on retiring boomers, but it doesn't wash. That boomer demographic anomaly was a birth boom from '46 to '64, a worker boom from '64 to '82, and we should have seen the retirement cause participation rate fall as a gradual decline starting in '93 and ending in 2011:
Whatever impact the boomers have had has been far overshadowed by the general economy.