I would not only say the rise in retirement demographics would be more sensitive to that change, but the rise in interest income is also associated with higher absolute money market fund yields, and the aggregate balances rising in money market funds would all play a role, yes.  Furthermore, when you tether the largest consumer debt to a 30-year fixed rate that doesn’t change when rates rise (mortgages), you don’t get the offset of rising interest expense to offset the rising benefit of rising interest income on cash holdings, hence a net benefit to discretionary cash flow.  That said, keep in mind that there has been a COLA adjustment to Social Security in the past few years to offset some of the effects of inflation for retirees.  Also, there has been a very large rise in total household net worth, of real estate values, of investable assets like stocks/bonds, so in terms of aggregate percentages, overall cash balances have kept pace.