Index funds are a winning investment strategy due to their low-cost, long-term success, and ability to capture the entire stock market's returns. By owning all of the nation's publicly held businesses at a very low cost, investors are guaranteed to capture almost the entire return generated by these businesses in the form of dividends and earnings growth. This approach is simple, yet highly effective, as it eliminates the risks associated with picking individual stocks, market sectors, and manager selection.

The best way to implement this strategy is to buy an all-market portfolio, also known as an index fund, and hold it forever. An index fund is a diversified portfolio designed to mimic the overall performance of the U.S. stock market or any financial market sector. This ensures that investors receive the market return, which has historically proven to be a successful long-term investment strategy.

One example of the success of index funds is the Vanguard 500 Index Fund, which has consistently outperformed the majority of actively managed funds over the past 25 years. This is due to the low costs associated with index funds, as they have minimal fees and turnover costs, allowing investors to keep more of their returns.

Another example is the Federal Thrift Savings Plan (TSP), which holds $460 billion of assets for the benefit of public servants and members of the armed services. The TSP predominantly uses index funds as its investment strategy, further demonstrating the effectiveness of this approach.

In conclusion, index funds offer a winning investment strategy by providing low-cost, long-term success, and capturing the entire stock market's returns. By owning an all-market portfolio and holding it for a lifetime, investors can eliminate unnecessary risks and achieve consistent market returns.