Can Flexible Trading Give You An Edge On Index Fund Returns?

Many investors today own index funds, whether they realize it or not. Index funds have become one of the most popular investment vehicles in the world because they offer broad diversification, low costs, and a simple way to invest in the market.

But behind the scenes, there is an often-overlooked process that can create costs for investors: index reconstitution.

Let’s start with the basics.

An index is simply a list of investments that meet certain criteria. The S&P 500, for example, is a list of approximately 500 large U.S. companies. An S&P 500 index fund seeks to own those same companies in roughly the same proportions as the index itself.

The goal of an index fund is not to outperform the index; it’s to match it as closely as possible.

The difference between a fund’s return and the return of the index it follows is called tracking error. A fund manager with low tracking error is doing a good job of staying in sync with the index. Because investors expect index funds to mirror their benchmarks, managers often go to great lengths to keep tracking error as close to zero as possible.

That sounds reasonable, but sometimes it creates an interesting challenge.

Recently, there has been significant discussion about the IPO of SpaceX. Once a company becomes publicly traded and eventually qualifies for inclusion in various stock market indexes, index providers may decide to add it to their lists. When that happens, index funds that track those indexes will need to buy shares of the company. That is how most people who own mutual funds end up with companies like SpaceX in their portfolios; fund managers buy shares, adding them to their index funds.

And they won’t be the only ones.

This brings us to index reconstitution.

Periodically, index providers review the companies included in their indexes. Companies may be added, removed, or moved between categories based on factors such as size, profitability, or liquidity. This update process is called reconstitution.

When a reconstitution occurs, index funds must adjust their holdings to match the new index composition. If a company is added, index funds buy it. If a company is removed, index funds sell it.

The challenge is that thousands of funds may be trying to make the same trades at nearly the same time.

Imagine a popular concert goes on sale and thousands of people try to buy tickets at once. Demand surges and prices rise. Financial markets work similarly. When many investors suddenly want to buy the same stock, prices can be pushed higher. When many investors are trying to sell, prices can be pushed lower.

Research has consistently found that stocks being added to major indexes often rise in price before and around their addition date. Stocks being removed frequently experience the opposite effect. In other words, investors who are required to trade on a specific date may end up buying after prices have already been bid up or selling after prices have already been pushed down.

This is one of the hidden costs of strict index tracking.

To be clear, this doesn’t mean index funds are bad investments. For many investors, they remain an excellent choice. However, it does highlight the difference between a strategy that must follow an index exactly and one that has flexibility in how it implements trades.

This is where firms such as Dimensional Fund Advisors (DFA) and others take a different approach.

Rather than attempting to perfectly track a published index, DFA builds portfolios designed to target specific areas of the market, such as smaller companies, value stocks, or companies with higher profitability. Because the firm is not trying to match an index on a particular day, its trading team has more flexibility regarding when and how trades are executed.

If a stock is being added to an index and demand is pushing the price higher, DFA does not have to join the crowd immediately. The firm can evaluate whether waiting may result in a better purchase price. Likewise, if a stock is being removed from an index and sellers are flooding the market, DFA may be able to avoid selling into temporary price pressure.

Think of it like shopping. If everyone rushes to buy the same item during a shortage, prices tend to rise. A patient shopper who can wait for inventory to return often gets a better deal. The same principle can apply in financial markets.

Most investors focus on visible costs such as expense ratios and trading commissions. Those costs matter. But implementation costs, the costs created by how and when trades occur, matter too.

While no investment strategy can eliminate all costs, flexibility can be valuable. By avoiding the need to trade at the exact moment an index changes, portfolio managers may be able to reduce unnecessary trading costs and keep more of a portfolio’s return working for investors.

Sometimes, successful investing isn’t just about what you own. It’s also about how you buy and sell it.