The S&P 500 has the hiccups. How investors should think about long-term returns.

Subscribe to enjoy similar stories. Let’s not call this a crisis of confidence in the S&P 500 index—at most, it’s a hiccup amid hallelujahs. The index was recently down slightly year to date but has still more than tripled investor money over the past decade.

There are anxieties for those who know where to look for them, however. This year, the S&P 500 Equal Weight index is doing better than the regular index, which is dominated by tech behemoths. Is that a change in leadership? Defensive sectors are rallying.

Healthcare, one of last year’s worst performers, is this year’s best. Value stocks outperformed growth by 3.9 percentage points in February, one of the top 5% of months for relative value returns going back to 1979, according to BofA Securities. Meanwhile, shares in Europe and China are outperforming the U.S.

this year. All of this will leave indexers torn over whether to fiddle with their fund mixes. Three U.K.

professors have released a report that doesn’t address this topic directly, but offers clues to how investors should think about long-term returns. Paul Marsh and Mike Staunton at London Business School, and Elroy Dimson at Cambridge University, compiled evidence on the exploits of stocks, bonds, bills, currencies, and consumer prices across countries and time periods, including ones that Wall Street doesn’t typically include in its glossy brochures. The three presented their findings in a book near the turn of the millennium called Triumph of the Optimists: 101 Years of Global Investment Returns, and have since offered yearly updates, with the latest, sponsored by Swiss bank UBS, including 125 years of data.