Adjust a US dollar amount for inflation between two dates ('what is $100 in 1990 worth today?'). Pass amount, from (YYYY-MM-DD or YYYY), and optional to (defaults to the latest CPI month). Uses CPI-U (CPIAUCNS — the same not-seasonally-adjusted all-items index as the official BLS inflation calculator), data back to 1913. Returns the inflation-adjusted amount, cumulative inflation %, annualized rate, and the CPI index values used on each date. Source: BLS CPI via FRED (St. Louis Fed).