An issue quite analogous to depreciation is depletion. For businesses that operate by extracting resources from the ground, surely one of their most important assets is the expected amount of oil, coal, diamonds, or whatever-it-might be that is still down there, yet to be extracted, on the land owned or leased by the company for this purpose. Over time, as oil [let us say] is removed, necessarily the remaining oil under there is depleted. The issue has often been politically contentious. Indeed, references to the oil depletion allowance in various stages of its development run like a Wagnerian motif through the various volumes of Robert Caro’s work on the life and times of Lyndon Johnson, who as both Representative and Senator from the oil-rich state of Texas was a stalwart defender of a very generous allowance for the tax accounting books, one which does not have to be duplicated in the financial accounting books. But let’s stick to the latter. One way in which account...