To be sure, instead of being wrong, all three of these indicators may just be early. But the divergence is a reminder to investors that nothing should be viewed in a vacuum. Manufacturing now makes up just 11% of gross domestic product in the U.S., the smallest share since 1947. And academic studies suggest the economy and stocks have virtually never been more disconnected.

A working paper by faculty from the MIT Sloan School of Management, the Haas School of Business at the University of California Berkeley, and New York University, finds that over the past three decades, economic growth has accounted for just 24% of share-price appreciation, compared with 92% for the 36 years prior.

Rather, what the authors call “factor share shocks” -- mainly the fruits of innovation, such as changes in the concentration of industries and growth of technology -- have been the “engine of market growth,” accounting for more than half the rise in more recent years.

Technological change and the rising sway of intangible assets like intellectual property have altered the market in countless ways. Combined, the value of the two largest American companies now exceeds that of the entire Russell 2000. Almost a quarter of the S&P 500 is now technology stocks, more than triple the share three decades ago. Last year, a quarter of the benchmark’s returns came from five companies alone -- Apple Inc, Microsoft Corp, Alphabet Inc, Facebook Inc, and Inc.

Maybe there’s a better way, then, to use certain pockets of the stock market as a window into the economy and a harbinger of what’s to come for equity prices. Some investors point to semiconductors as a proxy for growth, since they’re used in products from computers to cars to household appliances.

“The modern economy is powered by semiconductors,” said Tom Essaye, a former Merrill Lynch trader who founded “The Sevens Report” newsletter. “Semiconductors are extremely important and that’s one of the things I put, from a short-term standpoint, on the top of my screens to watch as far as general market momentum.”

Still, Essaye isn’t ready to toss Dow Theory from his toolkit.

“Of course the economy has changed a lot since Dow Theory was created 100 years ago,” he said. “But at the same time, it’s still one of the oldest and most time-tested technical tools that we have.”

This article was provided by Bloomberg News.

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