Strategies and ToolsMar 31, 20265 Min

How Index Construction Shapes ETF Performance

When most people think of exchange-traded funds (ETFs), they think about simplicity, diversification, and cost-effectiveness. ETFs have become one of the most sought-after investment options globally because they allow people to invest in entire markets, rather than individual stocks.

Often investors focus on an ETF’s name, theme, or past performance (which is not indicative of future results), but overlook one critical factor: index construction. The truth is that index construction has a huge impact on the performance of ETFs.

In this blog, we will discuss what index construction entails, its importance, and how it is a crucial part of determining the performance of the ETFs that are linked to these indices. This discussion is general in nature and does not take into account any individual’s investment objectives, financial situation, or needs.

What is Index Construction in ETFs?

Index construction is the set of rules and processes involved in creating a benchmark. A portfolio of securities that symbolises a market, industry, or investment strategy. An index is not simply a random assortment of stocks; it is a strategic portfolio of securities that symbolises a specific part of the financial universe.

As per the industry, an index is a portfolio of securities that includes a selection of securities governed by a unique set of rules and criteria. These rules include everything from selection and weightages to rebalancing intervals and liquidity requirements. Knowledge of these rules can help explain why different ETFs, even those that track the "same market," can act so differently.

In the case of ETFs that track an index, the index is essentially the genetic code of the ETF. The index instructs the ETF on which securities to own, how much to allocate to each, and when to rebalance the portfolio. However, ETFs may not perfectly replicate index performance due to fees, costs, and tracking differences.

Why Index Construction Matters for ETF Performance?

Most ETFs are passive, meaning they don’t try to beat the market. They aim to replicate the performance of a benchmark index. But that’s easier said than done. There is no guarantee that an ETF will achieve its investment objective or fully replicate the performance of its underlying benchmark.

Weighting Schemes Affect Performance and Risk

One of the main differences between indices is how they weight their components.

• Market Capitalisation Weighting: This is the most popular method of weighting. The weight of each stock in the index is determined by its total market value. Big stocks have more influence on the index performance than smaller stocks. While commonly used, this method also causes the index to be dominated by a few giant stocks.
• Equal Weighting: Each stock has an equal weight, regardless of its size. This gives smaller stocks more influence on the index performance. This may result in higher volatility compared to market-cap-weighted indices.
• Capped Indices: In this method, the weight of each stock is capped. This prevents the index from being dominated by a few stocks.

Each weighting method provides a different set of performance and risk profiles. For instance, a market-cap-weighted index may perform better when large stocks perform well and vice versa. Performance outcomes depend on market conditions and are not guaranteed.

Constituent Selection and ETF Exposure

Another key aspect of index creation is eligibility criteria, which determine which companies are eligible for inclusion in the index and on what grounds. Some indices are broad market exposure indices, while others are niche:

• Some are based on size (large-cap vs small-cap)
• Some are sector-specific (tech, healthcare, energy)
• Some go further and take into account financial characteristics such as value or momentum

This has an impact on the performance of the ETF in various market conditions. An index that tracks growth stocks may perform better in a bull market but may perform differently in a bear market. An index that tracks value stocks may provide different return patterns depending on market cycles. Market conditions are unpredictable and different strategies carry different risk levels.

Rebalancing, Turnover, and ETF Performance

Indices are not fixed. Each year, most indices are rebalanced. This involves stripping stocks that no longer qualify and adding new ones that qualify.

When an ETF must sell and buy stocks to keep up with these changes, it results in trading costs and possible tax triggers. This can be costly, which can negatively impact the performance of the ETF compared to the underlying index. Investors should review the ETF’s prospectus for details on fees, charges, and associated risks.

Some indices tend to change often, resulting in high turnover costs for the ETFs that track them. Others have rules that remain unchanged, resulting in low turnover costs and often different performance.

Liquidity Rules in Index Construction

Another important aspect of a well-structured index is liquidity. This refers to the ease with which a stock can be bought or sold without influencing the stock price. If illiquid stocks are part of an index, it could result in the ETF having difficulty trading these stocks effectively. In stressed market conditions, liquidity risks may increase and impact execution prices.

What Investors Should Check Before Choosing ETFs

If you are constructing a portfolio that involves ETFs, here are three things you should consider when analysing index construction. These considerations are general guidelines and should not be interpreted as personalised investment advice.

Read the Index Methodology

When analysing an ETF, do not simply focus on the name of the ETF. Instead, focus on the index that the ETF tracks. How is the index weighted? What are the rules for inclusion and exclusion of stocks in the index?

Check Turnover and Trading Costs

If an ETF tracks an index that rebalances regularly, the ETF may pay higher trading costs. These costs can negatively affect the net performance of the ETF, particularly over the long term.

Consider Risk and Exposure

Two ETFs that track the same market can have different risk profiles during stressful times. When you take a closer look at index construction, you gain a better understanding of these risk profiles. All investment decisions should be based on a careful assessment of risks and suitability.

Final Thoughts

Behind every ETF is a formula, a set of rules that dictate how it’s created. This formula is called the index construction methodology, and it’s a crucial part of determining how an ETF will perform. It’s not just about what’s inside the ETF, but also how it will act over time.

Knowing the rules is crucial for any investor who wants to think beyond just picking an ETF based on its name or popularity. If you want to make more informed ETF decisions and improve your ETF performance over time, start by understanding how indices are built. You may explore available products and services on Dealing.com’s platform, subject to your own assessment and independent advice where appropriate.

Disclaimer: This content is for educational purposes only and does not constitute investment advice, personal recommendations, or a solicitation to buy or sell financial instruments. All investments involve risk, including potential loss of capital. Investors should consult professional financial advisors and consider their personal circumstances before making any investment decision.