“Make the very wealthy begin to pay their fair share.” That was President Biden’s response when asked at last month’s presidential debate what he would do to address the looming insolvency of the Social Security trust fund. Combined with his opposition to benefit reductions of any kind, the implication is that Social Security’s finances should be stabilized by taxing the rich alone. In practice, this tax-only approach is like trying to patch a cracking dam with duct tape. Indeed, rather...