WHILE supply-side catechism insists that lower taxes are a growth tonic, the theory also argues that if you want less of something, tax it more. The economy desperately needs less of our bloated, unproductive and increasingly parasitic banking system. In this respect, the White House appears to have gone over to the supply side with its proposed tax on big banks, as it scores populist points against the banksters, too.

Not surprisingly, the bankers are already whining, even though the tax would amount to a financial pinprick  a levy of only 0.15 percent on the debts (other than deposits) of the big financial conglomerates. Their objections are evidence that the administration is on the right track.

Make no mistake. The banking system has become an agent of destruction for the gross domestic product and of impoverishment for the middle class. To be sure, it was lured into these unsavory missions by a truly insane monetary policy under which, most recently, the Federal Reserve purchased $1.5 trillion of longer-dated Treasury bonds and housing agency securities in less than a year. It was an unprecedented exercise in market-rigging with printing-press money, and it gave a sharp boost to the price of bonds and other securities held by banks, permitting them to book huge revenues from trading and bookkeeping gains.

Meanwhile, by fixing short-term interest rates at near zero, the Fed planted its heavy boot squarely in the face of depositors, as it shrank the banks’ cost of production  their interest expense on depositor funds  to the vanishing point.