The blended annual rate for 2021 is the weighted average of the rates for each year in the period. The weighting is based on the number of years in each rate period. For example, if the rates for 2020 and 2021 are both 3%, the blended rate would be 3% for both years. If the rates for 2020 and 2021 are 5% and 3%, respectively, the blended rate would be 4%.