Surpluses, deficits, and asset reserves
The difference between total income and total cost for a particular period of time is
the net increase in the trust fund for that period. If this amount is positive,
we say the fund had a surplus; if negative, the fund ran a deficit.
The sum of all surpluses and deficits since the beginning of the
program equals the asset reserves of the trust funds.
Almost all trust fund asset reserves are invested in securites backed by
the full faith and credit of the Federal government. Data on such
investments are updated monthly