First read Tyler on the practical difficulties implementing a tax on unrealized capital gains!

I have a different argument that I rarely see discussed. A significant fraction of what we call capital gains is due to variation in the discount rate rather than variation in income. Take the simplest Gordon model of stocks P=D/r where D is the annual dividend and r is the discount rate. If D=100 and r=.1, for example, then the stock is worth 100/.1=$1000. Now suppose people become more patient and the discount rate falls to .05 then P=$100/.05=$2000. The stock price doubles, a massive capital gain. But notice that income hasn’t gone up at all. It’s still D per year. Income hasn’t gone up and lifetime consumption possibilities haven’t gone up. Ultimately, we want to tax consumption so we should not be taxing “capital gains” which reflect changes in discount rates rather than changes in

Keep reading this article on Marginal Revolution.