Low interest rates and a rigid rate structure have hurt the mother of all retirement annuity gorillas. The giant Federal Old-Age and Survivors Insurance (OASI) trust fund — the fund that makes Social Security retirement benefits payments — is reporting a $22 billion operating loss for 2018 on $831 billion in revenue, compared with $26 billion in operating earnings on $826 billion in revenue for 2017. The OASI trust fund backs its Social Security retirement benefits obligations with a portfolio of $2.8 trillion in government bonds. The size of the portfolio held steady between 2017 and 2018. The bonds in the portfolio in 2018 paid interest rates ranging from 1.375% to 5.25%, and the average rate increased to 2.875% for bonds purchased in 2018, from 2.25% in 2017. But, because the overall average portfolio yield is continuing to fall, bond interest revenue fell 3%, to $81 billion. Benefits payments, meanwhile, increased much faster than payroll tax revenue. Gridlock in Washington could change things, but, in the past, the trust fund "depletion dates," or dates when program funds empty out, have served mainly to focus congressional attention on passing rescue bills. For insurance lobbyists, the major significance of that activity is that Medicare and Social Security rescue bills often end up serving as tugboats for moving other, less glamorous financial services legislation through Congress. For a look at more OASI financial details, see the data cards in the slideshow above. The Social Security program trustees' reports and related documents are available here.   READ MORE: Social Security's about to pay out more than it takes in Alicia Munnell: The Social Security fix nobody wants Ward off clients' retirement crisis with Social Security talk