This section contains answers to questions on SSDI and SSI eligibility, as well as the disability application and appeals process .
Social Security Disability Insurance (SSDI)
Your SSDI benefits are based on the amount of income on which you have paid social security taxes. Your average earnings are called your Average Indexed Monthly Earnings (AIME). Using your AIME, the SSA will calculate your Primary Insurance Amount (PIA). As of 2014, the PIA is calculated by taking 90% of AIME under $816, 32% of AIME between $816 and $4917, and 15% of AIME greater than $4917. The final PIA amount is the maximum amount of SSDI benefits that you are entitled to.
It's based on your entire life's payments into SS.
If you made, on average (and I'm not sure how the months when one doesn't work are calculated in the average), $5500/mo, I believe your monthly benefit would be:
(.9 * 816) + (.32 * (4917-816)) + (.15 * (5500-4917) = 2134.17/mo.
Though I'm also not sure how the AIME formula actually works, so ... YMMV.
Found this:
Up to 35 years of earnings are needed to compute average indexed monthly earnings. After we determine the number of years, we choose those years with the highest indexed earnings, sum such indexed earnings, and divide the total amount by the total number of months in those years. We then round the resulting average amount down to the next lower dollar amount. The result is the AIME.