What Is the Law of Large Numbers?

The performance of your stock portfolio is more likely to align with the market’s average return when you diversify.

When investing, your capital is at risk. The value of your investments can go down as well as up and you may get back less than you put in.

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Ever felt like the stock market is an unpredictable game of chance, with your hard-earned investments caught in a whirlwind of uncertainty? Fear not, dear investor! The law of large numbers is here to pacify the chaos of unruly short-term moves and help bring order to your financial feats.

What’s the big idea behind this soothing principle?

Grasping the law of large numbers is like unlocking a secret code that reveals the inner workings of the stock market over time. By appreciating this tenet, you’ll learn that the performance of your stock portfolio is more likely to align with the market’s average return as the number of stock tickers goes up.

Also, there will be sudden twists and turns along the way for almost every particular stock, portfolio, sector, or entire economy — but those temporary moves are easily forgotten when you invest for the long term. The unpredictable short-term dips and jumps tend to balance each other out, although the deck is stacked in favour of growth on a large scale.

However, don’t mistake this basic guideline for a foolproof recipe for success. It doesn’t guarantee riches, and factors like market conditions and company performance still play major roles in your returns. A truly successful investor needs a calm temperament and many years of patient portfolio management. Nonetheless, it’s an invaluable ally in helping investors make informed decisions, hand-in-hand with other trusty sidekicks like risk management and diversification.

Unleashing the power of the law of large numbers

Ready to harness the law of large numbers to boost your investment strategy? Here are some pearls of wisdom to help you navigate the stock market storm:

  • Diversification is your safety net: Don’t walk a financial tightrope by investing in just one stock. Instead, you should make many investments spread across various industries and asset classes to minimise risk.
  • Keep a long-term mindset: Remember that the law of large numbers works wonders over time. Stay patient, and don’t let short-term market turbulence hold too much sway over your investment decisions.
  • Manage risk like a master: Understand your risk tolerance and invest accordingly. Risk is inevitable, but you can mitigate it with a well-rounded investment strategy, and that includes relying on the law of large numbers.

Warren Buffett’s trust in index-tracking ETFs

There’s no denying the volatility-cooling power of the law of large numbers. Even the Oracle of OmahaBerkshire Hathaway CEO and Chairman Warren Buffett, entrusts millions of dollars to index-based funds and exchange-traded funds. That choice speaks volumes since Buffett’s skill at hand-picking specific stocks is legendary.

In particular, Buffett trusts the Vanguard S&P 500 ETF (NYSE:VOO) and the SPDR S&P 500 ETF Trust (NYSE:SPY) to deliver inflation-beating results in the long run with minimal fuss and worry. These sector-leading ETFs track the broad S&P 500 market index with high accuracy and negligible management fees, offering instant diversification by investing in a wide range of stocks through a single ticker. And here in the UK, investors have even more indices to pick from, including the FTSE 100 and FTSE 250.

In the unpredictable stock market, index funds and index-tracking ETFs provide investors with a no-brainer way to benefit from the law of large numbers. By investing in a vast array of stocks at once, the influence of individual stock fluctuations is diminished, leading to a more stable and predictable return over time. You can still try to beat the market with surgical accuracy in your individual stock choices, but it never hurts to have a robust foundation of market-matching assets, too.

This is the law of large numbers in action, calming the stormy waters of volatility and guiding investors toward their financial goals.

In conclusion, while the law of large numbers may not be a fail-safe formula for stock market success, it’s an invaluable ally in making sense of the market’s unpredictable ups and downs. Keep it in your investing arsenal, and you’ll be better equipped to tackle the stock market with confidence.

This article contains general educational content only and does not take into account your personal financial situation. Before investing, your individual circumstances should be considered, and you may need to seek independent financial advice.  

To the best of our knowledge, all information in this article is accurate as of time of posting. In our educational articles, a "top share" is always defined by the largest market cap at the time of last update. On this page, neither the author nor The Motley Fool have chosen a "top share" by personal opinion.

As always, remember that when investing, the value of your investment may rise or fall, and your capital is at risk.