Robert J. Walker ("Supply Side: Inflated Expectations," Free for All, Aug. 24) continues in The Post's tradition of taking cheap shots at supply-side economists. This is all good-natured fun and games inside the Beltway. However, the real game goes on out in the hinterland, where the voters know full well what the supply-side tax cuts have meant to them. Their real per-capita disposable incomes have increased by almost 10 percent since installation of the Reagan tax cuts in 1982. This compares with the paltry 1 percent rise in the last two years of the Carter administration. On top of this, median real family income rose 3.3 percent in 1984, the fastest rise since 1972.

What Walker conveniently fails to mention is that since 1983 tax revenues have increased by 23 percent. Tax revenues rose at an 11 percent rate in 1984, and they are now increasing at an 11.3 percent rate over last year. In fact, tax revenues are increasing three times faster than the rate of inflation.

Moreover, as the supply-siders predicted, the rich are paying more taxes than ever before. In 1982, the tax burden of those with incomes above $500,000 increased by 25 percent. By 1983 this group was bearing almost twice as much of the overall tax burden as before the Reagan cuts.

An objective look at the statistics reveals that our deficit problem is not a lack of tax revenues but rather the unwillingness of Congress to stop the explosion of federal spending.