Is Now the Right Time to Invest in the S&P 500?

Last week, the S&P 500 index, which comprises the 500 largest U.S. companies by market capitalization, reached a new all-time high, hitting $5,341.88 during intraday trading on Thursday, May 23.

Warren Buffett has long recommended an S&P 500 index fund as the ideal investment for those who don't have the time to analyze individual stocks in depth. The recent milestone seems to support his advice. However, with the stock market at a new peak, enthusiasm for AI potentially becoming excessive, and both interest rates and inflation remaining persistently high, is now truly the best time to invest in the S&P 500?

For those wary of the markets, there are numerous reasons to hesitate before buying into stock market averages. The S&P 500, a market-cap weighted index, is heavily influenced by large technology companies that have seen substantial gains recently, buoyed by a bull market that began in October 2022. Several factors have propelled these tech giants to new heights: interest rates seem to have peaked, inflation has dropped from its high of 9.1% in June 2022 to just 3.4% last month, and the surge in artificial intelligence has provided significant momentum.

It's not just Nvidia (NVDA 6.79%) reaching new peaks, with a staggering market cap of $2.6 trillion and a high P/E ratio of 62. Many cloud giants and related semiconductor stocks have also soared, driven by strong growth expectations. But will this growth persist indefinitely? AI investments must ultimately prove their worth to companies and consumers. Currently, companies are spending unprecedented amounts on AI chips and data centers to avoid falling behind. This situation is reminiscent of the dot-com boom in the late 1990s, which led to an epic crash in 2000. The tech-heavy Nasdaq Composite dropped 76.8% from peak to trough, while the S&P 500 fell by 49.1%.

Could the AI bubble burst similarly? AI momentum seems unstoppable, but few predicted the 2000 crash, believing internet hypergrowth would continue indefinitely. A slowdown in growth from an AI company could trigger a significant correction. While this might not happen soon, it’s a possibility.

Additionally, inflation impacts the Federal Reserve's decisions on interest rates, which in turn affect stock valuations and the economy. If inflation remains "sticky" and exceeds expectations, the Fed might keep interest rates higher for longer to meet its 2% target. This scenario poses a risk, as the S&P 500 is currently trading at a historically high valuation of 27.6 times trailing earnings, compared to the historical average of 16.1. If interest rates and inflation surge again, it could be a precarious time to invest in this frothy market.

On the flip side, renowned investor Peter Lynch famously noted, "there is always something to worry about" in the markets. Although the historical average P/E ratio of the S&P 500 is significantly lower than today's, the market has generally traded at a higher P/E ratio in recent years, averaging around 22.5 over the past decade. While this is still below current levels, it is much closer. Additionally, avoiding the stock market over the past ten years due to fears of high valuations would have resulted in missing out on 236% gains, including dividends.

Moreover, the average annual return of the S&P 500 from 1928 through 2023, since the Standard & Poor's index was first developed, is approximately 9.9% with dividends reinvested. Since the index expanded to 500 companies in 1957, the long-term annualized return has been an even better 10.3%. Certainly, there have been critical moments right before significant market crashes when investing would have seemed unwise. However, Ben Carlson, author of the blog A Wealth of Common Sense, highlights in his study that with a long enough time horizon, even investments made at market peaks before major crashes have yielded positive long-term results. Carlson examined hypothetical investments made just before eight of the market's worst crashes, from September 1929 to October 2007, prior to the Great Recession.

Five years later, three of those investments still produced positive results. Ten years out, six of the eight investments were profitable, with three delivering triple-digit gains. Twenty years after investing at these worst possible times, all eight were profitable, with all but the September 1929 investment yielding multi-hundred-percent gains. Prudent investing, however, is not solely about one-time, large investments. By consistently saving a portion of income and dollar-cost averaging into an index fund monthly, it's inevitable to invest before some market peaks but also benefit from subsequent downturns.

Market crashes are notoriously difficult, if not impossible, to predict. History shows that even investments made before the worst market peaks and crashes tend to recover over time, as the earnings of American businesses grow. Conversely, attempting to time the market can be costly, as demonstrated by those who have stayed out of the market for the past decade.

Therefore, the S&P 500 still seems like a wise buy today, even at its elevated valuation, provided there is a consistent investment plan with regular monthly, quarterly, or annual allocations.