Strategy. The Underlying Index is designed to measure the performance of the investment-grade segment of the U.S. municipal bond market as determined by ICE Data Indices, LLC, the index provider (the Index Provider). The Underlying Index includes municipal bonds from issuers that are primarily state or local governments or agencies whose interest is exempt from U.S. federal income taxes and the federal alternative minimum tax (AMT), but excludes bonds issued by U.S. territories, such as Puerto Rico (but debt issued by the District of Columbia is included), and certain other bonds as determined by the Index Provider. To be eligible for inclusion in the Underlying Index, each bond must be rated at least investment-grade (i.e., within the top four ratings categories … Show more… The Underlying Index is designed to measure the performance of the investment-grade segment of the U.S. municipal bond market as determined by ICE Data Indices, LLC, the index provider (the Index Provider). The Underlying Index includes municipal bonds from issuers that are primarily state or local governments or agencies whose interest is exempt from U.S. federal income taxes and the federal alternative minimum tax (AMT), but excludes bonds issued by U.S. territories, such as Puerto Rico (but debt issued by the District of Columbia is included), and certain other bonds as determined by the Index Provider. To be eligible for inclusion in the Underlying Index, each bond must be rated at least investment-grade (i.e., within the top four ratings categories as determined by a nationally recognized statistical rating organization (NRSRO)) and have a fixed coupon schedule. Each bond must also be denominated in U.S. dollars; generally must be a constituent of a deal where the original offering amount was at least $100 million; and generally have a minimum par amount of $10 million. In addition, to be included in the Underlying Index, each bond must have a minimum term to maturity or call date greater than or equal to one calendar day. The Underlying Index is governed by published, objective rules for security selection, exclusion, rebalancing and adjustments for corporate actions. The Underlying Index is reconstituted monthly. The Fund generally reconstitutes its portfolio in accordance with the Underlying Index. NTI uses a passive or indexing approach to try to achieve the Funds investment objective. Unlike many investment companies, the Fund does not try to beat the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued. NTI uses a representative sampling strategy to manage the Fund. Representative sampling is investing in a representative sample of securities that collectively has an investment profile similar to the Underlying Index. The Fund may or may not hold all of the securities that are included in the Underlying Index. The Fund reserves the right to invest in substantially all of the securities in its Underlying Index in approximately the same proportions (i.e., replication) if NTI determines that it is in the best interest of the Fund. Under normal circumstances, the Fund will invest at least 80% of its net assets (plus the amount of any borrowings for investment purposes) in debt instruments that pay interest that is exempt from regular federal income tax. Alternative minimum tax (AMT) obligations (also known as private activity bonds), which pay interest that may be treated as an item of tax preference to shareholders under the federal AMT, will not be deemed to be eligible debt instruments for the purposes of determining whether the Fund meets this policy. For shareholders subject to AMT, a portion of the Funds dividends may be subject to federal tax. As of May 30, 2025, the weighted average years to maturity of the bonds included in the Underlying Index ranged between six to 14 years. The Fund seeks to maintain an average maturity consistent with that of the Underlying Index. The Fund may also invest its assets in cash and cash equivalents, including shares of money market funds advised by NTI or its affiliates, futures contracts and options on futures contracts, as well as debt instruments or other securities not included in the Underlying Index, but which NTI believes will help the Fund track its Underlying Index. The Underlying Index is sponsored by the Index Provider, an organization that is independent of the Fund and NTI. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index. The Fund is non-diversified under the Investment Company Act of 1940, as amended (the 1940 Act), and may invest more of its assets in fewer issuers than diversified funds. The Fund will concentrate its investments (i.e., invest more than 25% of its net assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. The components of the Underlying Index, and the degree to which these components represent certain industries or sectors, may change over time. Show less