Others say the spike in beneficiaries is largely due to a 1984 policy change that expanded the qualifications for disability.
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Economists at the National Bureau of Economic Research, Mark Duggan and Scott Imberman released an analysis that found that relaxed medical eligibility criteria was the biggest factor driving the increase in disability beneficiaries.
Regardless of the reason, the number of beneficiaries has increased and naturally, so has spending. According to the Social Security Administration, spending on the program has more than tripled since 1983 from $43 billion to $139 billion, adjusted for inflation. It now accounts for about 20 percent of the Social Security Administration's total budget.
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Spending has ticked up so fast in recent years that revenue can't keep up. The government has paid out more than it has taken in every year since 2009, according to the Social Security Board of Trustees.
If the pattern continues and the program runs out of money by 2016, the millions of Americans collecting disability will see their benefits cut by at least 20 percent.