benchmark that is designed to track the U.S. long term tax-exempt bond market, including state and local general
obligation
bonds, revenue bonds,
pre-refunded
bonds, and insured bonds. National Customized Reference Benchmark is a broad, market value-weighted index, that is structured so that 90% of the market value measures the performance of the
tax-exempt
investment grade U.S. municipal bond market and 10% of the market value is either not rated or rated below investment grade. All bonds in the index are exempt from U.S. federal income taxes or subject to the alternative minimum tax.
For the
one-,
five- and
ten-year
periods ended December 31, 2020, the average annual total returns for the Bloomberg Municipal Bond Index were 5.21%, 3.91% and 4.63%, respectively. For the
one-year
period ended December 31, 2020, the average annual total return for the National Customized Reference Benchmark was
5.22
%.
The section of BlackRock Short-Term Municipal Fund’s Summary Prospectuses entitled “Key Facts About BlackRock Short-Term Municipal Fund — Performance Information” and the section of BlackRock Short-Term Municipal Fund’s Prospectuses entitled “Fund Overview — Key Facts About BlackRock Short-Term Municipal Fund — Performance Information” are supplemented as follows:
The Fund has changed the benchmarks against which it measures its performance from the S&P
®
Municipal Bond Index and the S&P
®
Limited Maturity Municipal Bond Index to the Bloomberg Municipal
1-5
Year Index and a customized index comprised of the Bloomberg
National Short
0-3
year maturities, excluding
non-investment
grade (the “Short-Term Customized Reference Benchmark”). Fund management believes the Bloomberg Municipal
1-5
Year Index and the Short-Term Customized Reference Benchmark more accurately reflect the investment strategy of the Fund. The Bloomberg Municipal
1-5
Year Index is a benchmark that covers the USD-denominated tax exempt bond market with maturities of between 1 to 5 years. The Short-Term Customized Reference Benchmark is a market value-weighted index containing all bonds in the investment grade U.S. municipal bond market that mature in 0 to 3 years and are exempt from U.S. federal income taxes or subject to the AMT.
For the
one-,
five- and
ten-year
periods ended December 31, 2020, the average annual total returns for the Bloomberg Municipal
1-5
Year Index were 2.83%, 1.98% and 1.87%, respectively. For the
one-year
period ended December 31, 2020, the average annual total return for the Short-Term Customized Reference Benchmark was 2.15%.