Stephen Entin, writing for the Tax Foundation, argues that switching to the chain-weighted CPI isn’t a good fix either for Social Security or the tax code. Excessive COLAs, Entin argues (correctly) aren’t the cause of Social Security’s funding shortfalls. Moreover, Entin points out, lowering inflation-adjustment of the income tax brackets generates “bracket creep,” where a greater share of worker’s incomes fall into higher tax brackets. This would increase taxes over time without any adjustments by Congress.
I made a similar argument here.