reference CPI-U: 1. The CPI-U index on the base-line-date of the private currency, or on a subsequent date; whereby the percentage difference in the reference CPI-U indexes is used to measure inflation or deflation. 2. The Reference CPI-U index for the Millennium Dollar®, which is 168.2. 3. The reference CPI-U index for the day on which you wish to calculate the indexed value of the Millennium Dollar®.