The whole purpose of a flat tax, à la 9-9-9, is to lower marginal tax rates and simplify the tax code. With lower marginal tax rates (and boy will marginal tax rates be lower with the 9-9-9 plan), both the demand for and the supply of labor and capital will increase. Output will soar, as will jobs. Tax revenues will also increase enormously—not because tax rates have increased, but because marginal tax rates have decreased.

By making the tax codes a lot simpler, we’d allow individuals and businesses to spend a lot less on maintaining tax records; filing taxes; hiring lawyers, accountants and tax-deferral experts; and lobbying Congress. As I wrote on this page earlier this year (“The 30-Cent Tax Premium,” April 18), for every dollar of business and personal income taxes paid, some 30 cents in out-of-pocket expenses also were paid to comply with the tax code. Under 9-9-9, these expenses would plummet without a penny being lost to the U.S. Treasury. It’s a win-win…

Still, a number of my fellow economists don’t like the retail sales component of the 9-9-9 plan. They argue that, once in place, the retail rate could be raised to the moon. They are correct, but what they miss is that any tax could be instituted in the future at a higher rate. If I could figure a way to stop future Congresses from ever raising taxes I’d do it every day of the week and twice on Sunday. Until then, let’s not make the perfect the enemy of the good.