Index Funds

A subset of mutual funds that enables investors to generate passive income.

Author: Jas Per Lim
Jas Per Lim
Jas Per Lim
Masters degree in Peking University, Undergrad in University of Bristol, work experience centers around South East Asian banks - Maybank & United Overseas Bank Worked across multiple areas of banking including Private Banking and Risk Management, but due to graduate in 2024 and seeking a corporate finance role at the moment
Reviewed By: Parul Gupta
Parul Gupta
Parul Gupta
Working as a Chief Editor, customer support, and content moderator at Wall Street Oasis.
Last Updated:March 29, 2024

What are Index Funds?

An index fund is a type of investment vehicle that enables investors to generate passive income.

Any fund works by pooling money from a large group of investors and subsequently investing them in various asset classes, including equities or bonds, depending on its strategy. 

It can be considered as a subset of mutual funds. However, a key difference between index and mutual funds is that the latter are actively managed, whereas the former are passively managed. 

When the NYSE has thousands of tradable securities, it can sometimes be difficult for new investors to decide which assets to purchase. This is why these investors turn to managed funds—they can have institutions work their money for a small fee. 

Generally, the strategy of this type of fund is not to buy and sell or constantly trade assets to generate returns. Instead, it aims to mirror the portfolio of an index (hence the name).

You can think of an index as a basket of assets where the performance of each asset is tracked.

Different index funds will track different indices, and it is up to the investor to decide which fund is suitable for their investing goals. Although the United State's most famous market index is the S&P 500, there are thousands of indices that all track a particular sector itself. 

Investors can purchase these funds through their brokerage accounts online (such as Vanguard or TD Ameritrade). Due to their benefits, they have become very popular investment vehicles over the past decade. 

Key Takeaways

  • Index funds are an investment vehicle that enables investors to purchase a basket of securities in a single share.

  • Index funds have become popular investment vehicles because they are passively managed and often provide better returns than actively managed funds.

  • Because index funds are passively managed, they often command lower expense ratios to investors.

  • While there are many similarities, index funds should not be confused with ETFs due to the critical differences in how they are traded.

Index Funds history

Stock markets are dynamic, with billions of dollars exchanging hands daily. Although it is impossible to understand or predict market movement completely, investors who could realize as much of it as possible would have the potential to generate serious profits.

Before indices were invented, it was difficult for investors to measure "the market" as a whole. Some stocks went up, others went down, but no one understood whether there was a bullish or bearish sentiment (among other things). 

This is why in 1896, a financial journalist named Charles H. Dow invented the Dow Jones Industrial Average (DJIA). He published the average price of 12 popular stocks, most of which were industrial companies because this was shortly after the Industrial Revolution.

The logic behind the DJIA was that investors could use the change in the average price to gauge the overall change in the market. In a way, if the DJIA was rising, investors took it as markets were rising, and vice versa. 

To this day, the Dow Jones Industrial Average index can still be found. However, its constituents are likely to have changed significantly from the past, and it now incorporates 30 stocks instead of just 12. 

Since then, many indices have been introduced, all representing a specified category. For example, the S&P 500 index tracks the performance of the top 500 companies in the United States and covers roughly 80% of the entire country's market capitalization

The FTSE 100 also tracks the top 100 publicly listed companies on the London Stock Exchange (LSE). However, indexes do not track only countries; you can find sector-related indices such as the Dow Jones US Technology Index, which covers the US tech industry.

Do professional money managers outperform stock market indices? 

Studies have shown that, on average, many hedge funds or institutional investors actually do not outperform the S&P 500. Perhaps they might get a good year where returns have skyrocketed. However, most of them post lackluster average returns in the long run.

Before mutual funds existed, investors invested in mutual funds, where a professional money manager selected securities to invest in. The fund manager consistently monitored and rebalanced its portfolio to increase returns. This is called active management. 

However, when studies have already shown that institutional investors cannot beat the market over the long term, many people questioned the functionality of mutual funds. 

Mutual funds often subject their investors to fees. For example, there will be sales commissions when an investor wants to buy into a specific fund. Furthermore, investors face a yearly expense ratio because they pay someone to manage their assets consistently. 

Investors are subjected to these charges regardless of whether the fund outperforms market indices, posts the same return, or even loses money. Therefore, when fund managers have historically shown poor track records, charging fees on top of damages to investors’ returns.

Subsequently, people realized that if even professionals lose to the market, why not simply invest in the market? This is where it came in - institutions started creating a fund that mirrors the constituents of a popular index and allows investors to buy into the fund. 

This way, if investors bought these funds, their returns would be similar to an index's. For example, there are index funds that track the S&P 500, and investors who buy into the fund would be able to gain returns that are very similar to the S&P 500. 

Because these types of funds mirror the portfolio of an index, there isn’t any portfolio manager to actively select the securities. Instead, the assets that go into the portfolio have been predetermined and don't change much. This is called passive management. 

index funds Advantages

This has become a very popular investment vehicle over the last decade (and with good reason). Many investors, including Warren Buffet, have been advocates of index funds and believe that this investment vehicle is the way to grow your wealth for most people.

Let’s go over some of the benefits behind this type of investment vehicle: 

1. Diversification

The benefits of diversification have been widely discussed in the financial world. Investors should never put all their eggs into one basket.

It allows investors to purchase a single investment vehicle representing a basket of securities. As a result, their exposure to each security is minimized, and they would never lose too much money even if a security drops significantly in value.

2. Passive management

Unlike active management, investors don’t have to consistently monitor their portfolio, look at a company’s latest earnings announcement, and frequently stare at price charts. Instead, simply buy, hold and forget. 


Passive management generally relies on the broader influx of capital to generate returns. If an investor sells his position in Tesla stock and reinvests it into Netflix, the S&P 500 index will still capture all that movement of capital (and so will the fund).

3. Low management fees

They generally charge lower expense ratios than mutual funds. This makes sense because there isn’t any portfolio manager actively selecting the securities that go into the portfolio. 

However, although management fees are lower, it isn’t zero. Because of this, these investment vehicles will always have returns that trail behind the index it mirrors, assuming there isn’t any tracking error.

4. Zero-knowledge requirements

investors don’t have to know a single thing about discounted cash flow, price-to-earnings ratios, or technical analysis to invest in these products.

This would be in contrast to the sales trader at Morgan Stanley or the asset manager at Fidelity, who spent hundreds of hours studying to pass the Chartered Financial Analyst (CFA) exam. Yet, it is likely that the market and that asset manager end up with an average return over the long run. 

Index funds Disadvantages

Even though index funds have many advantages, you should weigh any potential disadvantages before investing in this type of fund. The following are some things to consider:

1. Limited Growth Potential

Index funds are typically regarded as safe, but their extensive diversification also limits their prospective gains. Thus, index funds can safeguard your wealth.

Index funds generally give relatively modest returns as opposed to high-risk investments, such as cryptocurrency or NFTs, where big gains can be achieved.

While highly diversified products like index funds prioritize stability over large returns, cryptocurrencies have the potential to offer substantial rewards but also involve higher risk.

2. Lack of Flexibility

Index funds are limited in their ability to take advantage of certain investing opportunities. If your research identifies undervalued stocks, you will not be allowed to increase your exposure to equities inside an index fund.


You would have to buy the equities one at a time through your brokerage account, which would require more work and money.

3. Variable Returns

Not all index funds will produce returns that are as desirable as the S&P 500, which has historically produced an average annual return of about 10%.

A number of variables, including market circumstances, economic cycles, and the particular index that the fund is tracking, can affect how well index funds perform. It is advisable for investors to anticipate that their returns may not meet their expectations.

4. Market Conditions Vulnerability

Index funds rely on capital inflows and market expansion to produce returns. As a result, they are susceptible to market recessions and downturns.

Index fund prices may decrease in tandem with the overall market during economic downturns, possibly resulting in losses for investors. Although index funds provide long-term stability, investors should be mindful of their vulnerability to changes in the market.

Index Funds vs. Actively Managed Funds Vs. ETFs

Many amateurs will confuse this with mutual funds or ETFs. Many institutional investors also refer to certain investment vehicles interchangeably. Therefore, let’s review some differences between index, mutual, and exchange-traded funds.

Aspect Index Funds Actively Managed Funds Exchange Traded Funds
Management Approach Passively managed Actively managed Passively managed
Trading Frequency Once daily, based on NAV  Once daily, based on NAV Throughout trading day, like stocks
Price Determination    Based on NAV calculated at the end of the trading day Based on NAV calculated at the end of the trading day Market price fluctuates continuously during trading hours
Investment Objective     Mirrors performance of the specified index Managed by professionals to achieve specific objectives Mirrors performance of the specified index
Trading Mechanism    Traded once daily after the market closes Traded once daily after the market closes Traded throughout the trading day on exchanges

Example of Index Funds vs. ETFs

Confused? Don’t worry. Most people were at the beginning too. Let’s review some examples to see the difference between indexes and ETFs. This example will look at investment vehicles that track the S&P 500. 

Investment Vehicle Schwab S&P 500 Index Fund Vanguard S&P 500 ETF (VOO) Vanguard 500 Index Fund Admiral Shares (VFIAX)
Type Mutual Fund ETF Mutual Fund
Objective Mirror returns of S&P 500 Mirror returns of S&P 500 Mirror returns of S&P 500
Trading Mechanism Not traded on exchange, purchased through brokerage firms (e.g., Charles Schwab) Traded on exchange, like stocks Not traded on exchange, purchased through Vanguard
Market Price Fluctuation NAV-based, traded once daily The market price fluctuates continuously during trading hours NAV-based, traded once daily
Availability Limited to specific brokerage firms Widely available on exchanges Limited to Vanguard
Similarity to Stocks Not traded like stocks Traded like stocks Not traded like stocks
Licensing Restrictions Not applicable Not applicable Limited to naming restrictions, but mirrors S&P 500 returns

You can look at ETFs almost the same way you could stock- they are exchange-traded and have a market price. The critical difference is that they comprise more than one company.


Index funds replicate the performance of specific benchmarks, such as the S&P 500, providing investors with a diversified and passive investment strategy. Their simplicity, cheap management fees, and long-term stability in yielding returns have contributed to their increasing appeal.

When making investment decisions, investors should take into account potential drawbacks such as restricted growth potential, a lack of flexibility, and vulnerability to market conditions.

In contrast, professional managers actively oversee actively managed funds with the goal of outperforming market indices. Studies have revealed that a large number of these funds, meanwhile, are unable to regularly outperform the market, which makes investors doubt the efficacy of active management.

Exchange-traded funds, or ETFs, are exchanged throughout the trading day, much like stocks, but they differ from index funds in that they have a different trading mechanism and offer broader market exposure and passive management.

Investors can make well-informed selections that are in line with their investing objectives and risk tolerance by being aware of these distinctions.

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