(FORTUNE Magazine) – A fellow could get a touch of cognitive dissonance brooding over the material in Trends in Family Income: 1970-1986, the latest unsnappily titled publication of the Congressional Budget Office. The dissonance problem is somewhat as follows. Every time you turn on the tube, you get to observe a politico stating that we must instantly act to forestall penury among the old folks. But every time you point your nose toward Trends, you come across another reason for disbelieving the pol. Serious situation, eh? The CBO report looks to be one of the best studies of U.S. incomes now available. Unlike most such analyses, it is based on some important adjustments to the basic Census Bureau data. The adjustments take account of declines in family size during the period, and in looking at pre-1983 data they have gone to a more sophisticated measure of family living costs than was afforded by the CPI in those years (before it got overhauled). The message of the adjusted data is clear and consistent: Whether or not living in families, people over 65 have done astonishingly well in the Seventies and Eighties. Fortified by relentless rises in Social Security, senior families' median real income has risen by something like 54% since 1970. The gains for ''unrelated individuals'' were almost as high (50%). These gains were solid and virtually uninterrupted during the 16-year period, even though it included three recessions and double-digit inflation. Average annual gain for the seniors: 2.6% a year. No other age group was anywhere near that record. The figure for nonelderly married couples with children was 1.5% a year. For nonelderly unrelated individuals it was 1.2%. For young families (head under age 25), the change worked out to minus 1.2%. Against this background, is anybody proposing to relieve the country's budgetary miseries by holding back on Social Security increases? You better believe that's a rhetorical question. The Reagan Administration, which has just submitted a five-year defense program $220 billion lower than the amount deemed necessary three years ago, is boasting off in another corner that Social Security benefits for an average retired worker and spouse will soon be some 50% higher than in 1981. Dick Gephardt is proposing to increase spending on the elderly (and has cast himself as the logical successor to Franklin Roosevelt and Lyndon Johnson in this area). Jack Kemp looks to be even tougher in defending Social Security than the Democrats. Bob Dole says he is tougher than Jack Kemp. All of which is possibly not surprising, given the well-known overrepresentation of the old folks in the voting booth. And their notorious vengefulness toward solons considered disrespectful. When they can find any.