In a post from the Federal Reserve of Atlanta: How Has Disability Affected Labor Force Participation? they note, "How much can the change in demographics during the past decade explain the rise in disability or illness as a reason for not participating in the labor market? The answer seems to be: Not a lot."
They claimed in their post that "from the fourth quarter of 2007 through the end of 2013, the number of people claiming to be out of the labor force for reasons of illness or disability increased almost 3 million (or 23 percent)." But that number is actually much less.
Number of disabled workers only --> Awards (not applications) minus terminations for total in payment status:
As of Dec 2013: 8,942,584
From Dec 2007: 7,101,355
= 1,841,229 net increase on disability (not 3 million as stated in the Atlanta Fed post). Source: Social Security
The Atlanta Fed's article also goes on to say, "Only about one fifth of the decline in labor force participation as a result of reported illness or disability can be attributed to the population aging per se." So their fraction of (one fifth) would be even less --> It's actually 9.6% of those not in the labor force who receive disability.
NOTE: The 8.9 million total on disability (to date) is a very small fraction of the 92.5 million total that are currently not in the labor force. That is because offshoring to environmentally unregulated countries has been the primary cause that contributed to the lack of jobs that created the largest decline in the labor force participation rate.
Also, we have over twice as many high school graduates every year than we have people
retiring on Social Security. The increase of those in payment status for disability is minuscule compared to these demographics.
After being laid off during the Great Recession and collecting their maximum weeks of unemployment benefits, many 62 year-olds took early retirements. U.S. News reports that according to a 2011 Employee Benefit Research Institute survey, 68 percent of retirees ended up retiring before reaching age 65 (before qualifying for their full benefit amount). I suspect that after being laid off in 2008//2009 they were already "long-term unemployed" and unable to obtain another job when employers began hiring again. So when workers turned 62, they were forced to take a lower Social Security benefit. (The first Baby Boomer retired at 62 in 2008 and the First Baby Boomer turned 65 in 2011).
My other posts on this subject at the Economic Populist:
Record Number of Boomers Left the Labor Force: February 10, 2014
Long-Term Unemployed Baby Boomers in 2013: August 26, 2013
The Last Word on Social Security Disability: July 22, 2013
Report: Disability Claims and Awards Declined: July 19, 2013