CNN  — 

The US stock market has been on a rollercoaster during President Donald Trump’s second term. The S&P 500 posted its third-worst 100-day start to a presidential term in US history, only behind Gerald Ford and Richard Nixon.

The S&P 500 initially surged after Trump’s reelection in November on expectations for a pro-business boom. Yet as the president unveiled his plan for tariffs and has gone back and forth on trade policy, Wall Street has been shaken by historic levels of uncertainty and volatility.

CNN is tracking the S&P 500’s performance each day across Trump’s second term to see how it compares to past presidents since World War II.

As the benchmark US stock index, the S&P 500 tracks the 500 biggest public companies in the United States by market value. Even if you don’t own individual stocks, retirement plans like 401(k)s are invested funds that track the S&P 500, meaning you might be invested in these top companies through your employer.

About 62% of US adults held stocks in 2024, whether through an individual stock, a mutual fund or a retirement savings account, according to an annual Gallup survey.

Since the end of World War II, the S&P returned an average of 2.1% during a president’s first 100 days, according to Sam Stovall, chief investment strategist at CFRA Research.

An above-average return for the S&P during a president’s first 100 days corresponded with an average gain that year of 21.1%. Meanwhile, a below-average return for the S&P during a president’s first 100 days corresponded with an average loss that year of 5.5%.

“History is a guide, but it’s never gospel,” Stovall said.

Investors this year will be focused on how Trump’s tariffs might continue to impact the economy and markets.

“I think a lot of people on Wall Street were expecting tariffs to be more rhetoric than reality,” Stovall said. “In fact, it ended up being reality. We have yet to find out what the longer-term outcome will be.”