The present-day consumer price index does not meet this standard. In fact, the best available evidence suggests that there is virtually no chance that the CPI as currently published understates the rate of growth of the appropriate concept.
In other words, there is almost a 100 percent probability that we are overcompensating the average social security recipient for increases in the cost of living, and almost a 100 percent probability that we are causing the inflation-adjusted burden of the income tax system to decline more rapidly than I presume the Congress intends.