A Rare S&P 500 Signal Appears for the First Time in 36 Years. What Now?

A market signal not seen in 36 years of data has just appeared in the S&P 500. It points to something unusual going on beneath the surface of Wall Street’s largest index.

On November 2, the S&P 500 moved into extreme oversold territory at the same time as close to half of its members were overbought.

That is according to Bespoke Investment Group, which said the index closed more than two standard deviations below its 50-day moving average, a yardstick for how far prices have dropped from the recent trend.

Nonetheless, 46.8% of the S&P 500’s members sat in overbought territory.

Since 1990, five comparable episodes have taken place. In those previous instances, overbought stocks never accounted for more than 33.4% of the index.

What Lies Behind This Never-Before-Seen S&P 500 Signal?

The answer is rooted in the way the index is constructed.

Bigger companies exert more influence on the S&P 500. As a result, sharp falls in heavyweight names such as Nvidia, Alphabet and Meta can push the entire index down even while hundreds of other stocks are on the rise.

October offered a powerful illustration.

The conventional S&P 500 fell 0.9%, while its equal-weighted counterpart — where each member has similar influence — rose 5%.

That 5.9-percentage-point difference was the largest seen since April 2009.

Investors questioned the returns on heavy AI spending, yet nine of the 11 sectors advanced.

Which Companies Could Gain as This Rotation Unfolds?

The nascent shift favors businesses outside the AI trade.

• Energy producers Chevron and ConocoPhillips could keep attracting investment if oil prices hold up.
• Healthcare companies such as Eli Lilly and Johnson & Johnson may win support from investors looking for steadier earnings.
• Consumer staples stocks including Walmart could draw attention as investors trim exposure to costly technology shares.

Still, the gains racked up in October already make a reversal a real possibility.

The big question for investors is whether this rotation can last long enough to support a broader market advance, or whether cracks in Big Tech eventually spread to the rest of the market.