Consumer Price Index for All Urban Consumers (CPI-U) from U.S. Department Of Labor Bureau of Labor Statistics. This is a monthly time series from January 1913. Values are U.S. city averages for all items and 1982-84=100. Note that there are many price indices and this is only one of them (albeit the most standard and with the longest set of data).
Data is sourced from bls.gov and normalized into a CSV
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