Under the calm surface, however, there is furious paddling. Only once in the past 25 years have stocks swung about like this while the overall market stayed so placid. Traders in the options markets are betting on its continuing: Prices indicate the biggest swings in stocks for at least 10 years relative to the prevailing calm for the S&P 500.

One way to think about this is that, at a high level, investors think not a lot is going on. But when they look at particular stocks, the impact of the two-speed economy and excitement about artificial intelligence matter hugely. The result is far more stocks with 10% swings in a day over the past three months than at almost any other time when the market can barely get above an average move of 0.5%.

Investors widely agree that the big bout of inflation is over, that the economy will be neither so hot nor so cold that the Federal Reserve will have to make major changes, and that wars in the Middle East and Ukraine are contained.

"Not only is [the consensus among investors] stronger than usual, what everyone's talking about is things like, is inflation going to be 0.3% or 0.4%?" said Guy Miller, chief market strategist at Zurich Insurance.

Naturally, the S&P is serene.

At the same time, investors are trying to pick the winners and losers from higher-for-longer interest rates and AI. There are enough stocks that do well or badly from interest rates to move share prices around a lot, but they largely cancel out at the index level. This shows up in stock options that are priced for very low correlation between them—the lowest for the year ahead since at least 2006.

As for AI, the bet so far is about who the winners will be, with little evidence yet of who will lose. But hopes for AI have led to huge gains for the AI leaders, especially chip maker Nvidia, which has powered away from the rest of the market to become the second-biggest company by value. As a result, even when stocks are up, some are up far more than others.

This leads to a high level of what traders call dispersion, a measure of how much individual stocks move versus each other.