This index fund seeks to replicate the performance of a benchmark index representing the investment-grade portion of the U.S. municipal bond market. It achieves this by employing an indexing strategy designed to track the Standard & Poor’s National AMT-Free Municipal Bond Index, utilizing a sampling technique to align with key characteristics of the benchmark. All holdings are selected through this sampling process, ensuring that at least 80% of the fund's assets are invested in securities found within the index. Under typical circumstances, a minimum of 80% of the fund's assets will be dedicated to securities whose income is exempt from federal income taxes and the federal alternative minimum tax. A notable risk for the fund is that changes in interest rates can negatively impact it: rising rates may cause bond prices to fall, while declining rates could eventually reduce the fund's income. This fund may appeal to investors looking for potentially federal tax-exempt income who can tolerate moderate fluctuations in both price and income. Regarding 75% of its total assets, the fund is restricted from purchasing more than 10% of any issuer's outstanding voting securities, or investing over 5% of its total assets in a single issuer, unless doing so is essential to closely match its target index. These specific limitations do not extend to obligations issued by the U.S. government or its agencies.