Then, in 1926, came the loophole that has undoubtedly caused more gnashing of teeth among those not in a position to profit by it than any other—the percentage depletion allowance on petroleum, which permits the owner of a producing oil well to deduct from his taxable income up to 27½ per cent of his gross annual income from the well and to keep deducting that much year after year, even though he has deducted the original cost of the well many times over.
