S000005358 [Member] Investment Risks - EMERGING MARKETS EQUITY INDEX FUND

Mar. 31, 2026

EMERGING MARKETS RISK is the risk that emerging markets are generally subject to greater market volatility, political, social and economic instability, uncertain trading markets and more governmental limitations on foreign investments than more developed markets. In addition, companies operating in emerging markets may be subject to lower trading volumes and greater price volatility than companies in more developed markets. Emerging market economies may be based on only a few industries, may be highly vulnerable to changes in local and global trade conditions, and may suffer from extreme and volatile debt burdens or inflation rates. Companies in emerging market countries generally may be subject to less stringent regulatory, disclosure, financial reporting, accounting, auditing and recordkeeping standards than companies in more developed countries. As a result, information, including financial information, about such companies may be less available and reliable, which can impede the Fund’s ability to evaluate such companies. Securities law and the enforcement of systems of taxation in many emerging market countries may change quickly and unpredictably, and the ability to bring and enforce actions (including bankruptcy, confiscatory taxation, expropriation, nationalization of a company’s assets, restrictions on foreign ownership of local companies, restrictions on withdrawing assets from the country, protectionist measures and practices such as share blocking), or

to obtain information needed to pursue or enforce such actions, may be limited. Investments in emerging market securities may be subject to additional transaction costs, delays in settlement procedures, unexpected market closures, and lack of timely information.

FOREIGN SECURITIES RISK [Member]

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FOREIGN SECURITIES RISK is the risk that investing in foreign (non‑U.S.) securities may result in the Fund experiencing more rapid and extreme changes in value than a fund that invests exclusively in securities of U.S. companies, due to less liquid markets and adverse economic, political, diplomatic, financial, and regulatory factors. Foreign governments may impose limitations on foreigners’ ownership of interests in local issuers, restrictions on the ability to repatriate assets, and may also impose taxes. Any of these events could cause the value of the Fund’s investments to decline. Foreign banks, agents and securities depositories that hold the Fund’s foreign assets may be subject to little or no regulatory oversight over, or independent evaluation, of their operations. Additional costs associated with investments in foreign securities may include higher custodial fees than those applicable to domestic custodial arrangements and transaction costs of foreign currency conversions. Unless the Fund has hedged its foreign currency exposure, foreign securities risk also involves the risk of negative foreign currency rate fluctuations, which may cause the value of securities denominated in such foreign currency (or other instruments through which the Fund has exposure to foreign currencies) to decline in value. Currency exchange rates may fluctuate significantly over short periods of time. Currency hedging strategies, if used, are not always successful. For instance, forward foreign currency exchange contracts, if used by the Fund, could reduce performance if there are unanticipated changes in currency exchange rates.

GEOGRAPHIC RISK [Member]

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GEOGRAPHIC RISK is the risk that if the Fund invests a significant portion of its total assets in certain issuers within the same country or geographic region, an adverse economic, business or political development affecting that country or region may affect the value of the Fund’s investments more, and the Fund’s investments may be more volatile, than if its investments were not so concentrated in such country or region.

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CHINA INVESTMENT RISK is the risk associated with investments in companies located or operating in China, such as nationalization, expropriation, or confiscation of property; lack of willingness or ability of the Chinese government to support the economies and markets of the Greater China region; and considerable degrees of economic, political and social instability. Despite prior economic and trade reforms and the prior expansion of private ownership of companies in certain sectors, the Chinese government still exercises substantial influence over many aspects of the private sector and may own or control many companies, including by embedding Chinese Communist Party or People’s Armed Forces Department personnel in Chinese companies. In addition, the Chinese government continues to maintain a major role in economic policy making and may alter or discontinue economic or trade reforms at any time. Investors in Chinese markets generally experience difficulties in obtaining information necessary for audits of, investigations into and/or litigation against Chinese companies, as well as in obtaining and/or enforcing judgements due to a lack of publicly available information; and there are generally limited legal remedies for shareholders. Complex geopolitical tensions, internal social unrest or confrontations with other neighboring countries, including military conflicts may disrupt economic development in China and result in a greater risk of currency fluctuations, currency convertibility, interest rate fluctuations and higher rates of inflation. Export growth continues to be a major driver of China’s rapid economic growth. As a result, a reduction in spending on Chinese products and services, supply chain diversification or the institution of additional tariffs or other trade barriers, including as a result of heightened trade tensions between China and the U.S., or a downturn in any of the economies of China’s key trading partners may have an adverse impact on the Chinese economy. Additionally, the Public Company Accounting Oversight Board (“PCAOB”) has historically had difficulties inspecting audit work papers and practices of PCAOB-registered accounting firms in China with respect to their audit work of U.S. reporting companies. These difficulties may impose significant additional risks associated with investments in China, including with respect to the reliability of the audits and of the information about the Chinese securities or the potential delisting of a U.S.-listed Chinese issuer due to an inability to inspect the issuer’s accounting firm. Certain securities issued by companies located or operating in China, such as China A‑shares, are subject to trading restrictions and suspensions, quota limitations and sudden changes in those limitations, and operational, clearing and settlement risks. In addition, actions by the U.S. government, such as delisting of certain Chinese companies from U.S. securities exchanges or otherwise restricting their operations in the U.S., may negatively impact the value of such securities held by the Fund.

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SOUTH KOREA INVESTMENT RISK is that risk that South Korean issuers in which the Fund invests may subject the Fund to legal, regulatory, political, currency, security, and economic risks that are specific to South Korea. In addition, economic and political developments of South Korea’s neighbors, including escalated tensions involving North Korea and any outbreak of hostilities involving North Korea, or even the threat of an outbreak of

hostilities, may have a severe adverse effect on the South Korean economy. Additionally, South Korea’s heavy reliance on trading exports and the risk of disruptions or decreases in trade activity may negatively impact the South Korean economy.

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TAIWAN INVESTMENT RISK is the risk of investing in securities of Taiwanese issuers, and includes Taiwanese legal, regulatory, political, currency, and economic risks. Specifically, Taiwan’s geographic proximity and history of political contention with China have resulted in ongoing tensions between the two countries, which may materially affect the Taiwanese economy and its securities market. Investments in securities of Taiwanese companies are subject to Taiwan’s heavy dependence on exports. Reductions in spending on Taiwanese products and services, labor shortages, institution of tariffs or other trade barriers, or a downturn in any of the economies of Taiwan’s key trading partners, including the United States, may have an adverse impact on the Taiwanese economy and the values of Taiwanese companies.

DEPOSITARY RECEIPTS RISK [Member]

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DEPOSITARY RECEIPTS RISK Foreign securities may trade in the form of depositary receipts. In addition to investment risks associated with the underlying issuer, depositary receipts may expose the Fund to additional risks associated with non‑uniform terms that apply to depositary receipt programs, including credit exposure to the depository bank and to the sponsors and other parties with whom the depository bank establishes the programs, currency, political, economic, market risks and the risks of an illiquid market for depositary receipts. Depositary receipts are generally subject to the same risks as the foreign securities that they evidence or into which they may be converted. Depositary receipts may not track the price of the underlying foreign securities on which they are based, may have limited voting rights, and may have a distribution subject to a fee charged by the depository. As a result, equity shares of the underlying issuer may trade at a discount or premium to the market price of the depositary receipts.

TRACKING RISK [Member]

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TRACKING RISK is the risk that the Fund’s performance may vary from the performance of the index it tracks as a result of share purchases and redemptions, transaction costs, expenses and other factors. Market disruptions, regulatory restrictions or other abnormal market conditions could have an adverse effect on the Fund’s ability to adjust its exposure to required levels in order to track its Index or cause delays in the Index’s rebalancing schedule. During any such delay, it is possible that the Index, and, in turn, the Fund will deviate from the Index’s stated methodology and therefore experience returns different than those that would have been achieved under a normal rebalancing or reconstitution schedule.

SECTOR RISK [Member]

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SECTOR RISK is the risk that companies in similar businesses may be similarly affected by particular economic or market events, which may, in certain circumstances, cause the value of securities of all companies in a particular sector of the market to decrease.

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FINANCIALS SECTOR RISK is the risk that companies in the financials sector can be significantly affected by changes in interest rates, government regulation, the rate of corporate and consumer debt defaulted, price competition, and the availability and cost of capital, among other factors.

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INFORMATION TECHNOLOGY SECTOR RISK is the risk that securities of technology companies may be subject to greater price volatility than securities of companies in other sectors. These securities may fall in and out of favor with investors rapidly, which may cause sudden selling and dramatically lower market prices. Technology companies also may be affected adversely by changes in technology, consumer and business purchasing patterns, government scrutiny or regulation, legal action and/or obsolete products or services.

MID CAP STOCK RISK [Member]

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MID CAP STOCK RISK is the risk that stocks of mid‑sized companies may be more volatile than stocks of larger, more established companies, and may lack sufficient market liquidity. Mid‑sized companies may have limited product lines or financial resources, may be dependent upon a particular niche of the market, or may be dependent upon a small or inexperienced management group. Securities of mid‑sized companies may trade less frequently and in lower volume than the securities of larger companies, which could lead to higher transaction costs. Generally, the smaller the company size, the greater the risk.

INDEX RISK [Member]

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INDEX RISK is the risk that that the Fund would not necessarily buy or sell a security unless that security is added or removed, respectively, from the Index, even if that security generally is underperforming, because unlike many investment companies, the Fund does not utilize an investing strategy that seeks returns in excess of the Index. Additionally, the Fund rebalances its portfolio in accordance with the Index, and, therefore, any changes to the Index’s rebalance schedule will result in corresponding changes to the Fund’s rebalance schedule.

DERIVATIVES RISKS [Member]

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DERIVATIVES RISK is the risk that derivatives may pose risks in addition to and greater than those associated with investing directly in securities, currencies and other instruments, may be illiquid or less liquid, more volatile, more difficult to value and leveraged so that small changes in the value of the underlying instrument may produce disproportionate losses to the Fund. Derivatives are also subject to counterparty risk, which is the risk that the other party to the transaction will not perform its contractual obligations. The use of derivatives is a highly specialized activity that involves investment techniques and risks different from those associated with investments in more traditional securities and instruments.

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FUTURES CONTRACTS RISK is the risk that there will be imperfect correlation between the change in market value of the Fund’s securities and the price of futures contracts, which may result in the strategy not working as intended; the possible inability of the Fund to sell or close out a futures contract at the desired time or price; losses due to unanticipated market movements, which potentially are unlimited; and the possible inability of the Fund’s investment adviser to correctly predict the direction of securities’ prices, interest rates, currency exchange rates and other economic factors, which may make the Fund’s returns more volatile or increase the risk of loss.

VALUATION RISK [Member]

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VALUATION RISK is the risk that the sale price the Fund could receive for a portfolio security may differ from the Fund’s valuation of the security, particularly for securities that trade in low volume or volatile markets or that are valued using a fair value methodology. It is possible that the Fund could incur a loss because a portfolio security is sold at a discount to the value ascribed to it for purposes of calculating the Fund’s net asset value. Fair value methodologies may involve more subjectivity than the use of market quotations when fair valuing an investment. In addition, the value of the securities in the Fund’s portfolio may change on days when shareholders will not be able to purchase or sell the Fund’s shares.

SECURITIES LENDING RISK [Member]

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SECURITIES LENDING RISK is the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral.

MARKET RISKS [Member]

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MARKET RISK is the risk that the value of the Fund’s investments may increase or decrease in response to expected, real or perceived economic, political or financial events in the U.S. or global markets. The frequency and magnitude of such changes in value cannot be predicted. Certain securities and other investments held by the Fund may experience increased volatility, illiquidity, or other potentially adverse effects in response to changing market conditions, inflation, elevated levels of government debt, changes in interest rates, lack of liquidity in the bond or equity markets or volatility in the equity markets. Market disruptions caused by local or regional events such as financial institution failures, changes in trade regulation or economic sanctions, internal unrest and discord, war, acts of terrorism, the spread of infectious illness (including epidemics and pandemics) or other public health issues, recessions, the threat or occurrence of a government shutdown, or other events or adverse investor sentiment could have a significant impact on the Fund and its investments. During periods of market disruption or other abnormal market conditions, the Fund’s exposure to risks described elsewhere in this summary will likely increase.

Risk Lose Money [Member]

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As with any mutual fund, it is possible to lose money on an investment in the Fund.

Risk Not Insured Depository Institution [Member]

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An investment in the Fund is not a deposit of any bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation, any other government agency, or The Northern Trust Company, its affiliates, subsidiaries or any other bank.

Risk Nondiversified Status [Member]

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NON-DIVERSIFICATION RISK Under the 1940 Act, a fund designated as “diversified” must limit its holdings such that the securities of issuers which individually represent more than 5% of its total assets must in the aggregate represent less than 25% of its total assets. The Fund is “diversified” for purposes of the 1940 Act. However, in seeking to track its Index, the Fund may become “non‑diversified,” as defined in the 1940 Act, solely as a result of a change in relative market capitalization or index weighting of one or more constituents of the Index. A non‑diversified fund can invest a greater portion of its assets in the obligations or securities of a small portion of its assets in the obligations or securities of a small number of issuers or any single issuer than a diversified fund can. In such circumstances, a change in the value of one or a few issuers’ securities will therefore affect the value of the Fund more than if it was a diversified fund.