“The stock market is doing fine.”

Look at the S&P 500 and that seems pretty reasonable.

The index is still up roughly 12% this year. Despite surging interest rates, volatile oil prices and plenty of economic uncertainty, stocks have mostly held together.

But look underneath the index and you get a very different picture.

As of Tuesday afternoon, only 40.8% of S&P 500 stocks were trading above their 200-day moving average.

That means nearly 60% of the companies in the index are below one of the most commonly used measures of their long-term trend.

More interestingly, that is the lowest reading since May 6, 2025.

That date matters.

May 2025 was right after the tariff scare that rocked markets the previous month.

President Trump announced sweeping tariffs on April 2. Over the following two trading days, roughly $5 trillion of S&P 500 market value disappeared, and the Nasdaq fell into a bear market.

Then, on April 9, Trump announced a 90-day pause on many of the tariffs.

The S&P 500 surged 9.5% in a single day, its biggest gain since 2008.

So when market breadth was this weak in May 2025, it wasn't particularly surprising.

Stocks had just gone through a legitimate market panic.

Today?

The S&P 500 is still up double digits this year.

And yet the percentage of stocks in long-term uptrends looks about as bad as it did immediately after one of the biggest market scares of the past few years.

That’s worth paying attention to.

One reason this can happen is pretty simple.

The S&P 500 is weighted by market capitalization.

The bigger the company, the more it matters.

So a handful of enormous companies can have a disproportionate impact on the entire index.

If NVIDIA rises 3%, that matters a lot more to the S&P 500 than if a much smaller company falls 3%.

Multiply that across a handful of mega-cap stocks and you can end up with a strange situation:

The index looks healthy even while a large percentage of the stocks inside it are struggling.

That appears to be happening right now.

The S&P 500 itself was roughly flat for September heading into Tuesday, even though fewer than half of its components were above their 200-day moving averages.

In other words, the headline number is hiding a lot of weakness underneath the surface.

This is what investors mean when they talk about market breadth.

A broad rally means lots of stocks are participating.

A narrow rally means a relatively small group of stocks is doing most of the work.

Right now, this market looks increasingly narrow.

There are plenty of possible explanations.

The most obvious is interest rates.

The 10-year Treasury yield reached roughly 5.29% Tuesday, while the 30-year yield touched about 5.62%.

For the 30-year, that was the highest level since 2002.

Those numbers matter.

For most of the decade following the financial crisis, investors got used to extremely low interest rates.

Cash paid almost nothing.

Government bonds didn't pay much more.

That made stocks relatively attractive almost by default.

There was even an acronym for it:

TINA.

There Is No Alternative.

That argument becomes harder to make when investors can earn more than 5% on long-term U.S. government debt.

And higher rates don't just give investors another place to put their money.

They also affect companies.

A giant technology company generating tens of billions of dollars in cash doesn't necessarily care that much if borrowing costs rise.

A smaller company carrying lots of debt might care quite a bit.

If it has to refinance that debt at substantially higher rates, more of its cash flow goes toward interest payments and less goes toward everything else.

So it makes sense that a high-rate environment could create a growing divide between the strongest companies and everyone else.

This is where things get tricky.

It would be easy to look at that 40.8% figure and say:

“Only 40% of stocks are above their 200-day moving averages. The market is about to crash.”

That's not what the data tells us.

Weak breadth is a warning sign.

It is not a countdown clock.

Markets can remain narrow for surprisingly long periods.

And there are two ways this divergence can resolve.

The obvious bearish version is that the mega-cap stocks eventually fall and catch down to everything else.

But there's another possibility.

The weaker stocks could recover and catch up to the leaders.

Same breadth problem.

Very different outcome.

That's why market breadth is useful for understanding what is happening, but much less useful for telling you exactly what happens next.

Last spring, investors knew why breadth was terrible.

Markets had just been hit by a huge policy shock.

The S&P 500 lost trillions of dollars in market value in a matter of days as investors tried to figure out what sweeping tariffs would mean for inflation, corporate profits and economic growth.

Today's weakness is less obvious.

There hasn't been a comparable collapse in the headline index.

Instead, the pressure is showing up gradually underneath it.

Some stocks are doing extremely well.

Others are quietly rolling over.

And because the winners happen to be some of the largest companies in the world, the S&P 500 can continue looking relatively healthy.

That may be the most interesting thing about this market right now.

Yesterday I wrote about whether today's AI boom is starting to resemble the dot-com bubble.

My conclusion was basically this:

Maybe stocks are expensive.

Maybe AI expectations are too high.

Maybe we're due for a correction.

But today's valuations, profits and investor sentiment look very different from what we saw in 2000.

Today's breadth data adds another wrinkle.

The headline index may look strong.

That doesn't mean every stock underneath it is strong.

In fact, right now, most of them aren't.

The last time the percentage of S&P 500 stocks above their 200-day moving average was this low, investors were still recovering from the tariff panic of April 2025.

Today, there is no similar crash to point to.

The S&P 500 is still up about 12% this year.

Yet nearly 60% of the stocks inside it are below their 200-day moving averages.

Maybe those stocks are warning us that the headline index is eventually going to catch down.

Maybe they're simply taking a breather while the biggest companies continue carrying the market.

Or maybe the next move is a broadening rally where today's laggards start catching up.

Nobody knows.

But it does mean that looking at the S&P 500 alone is giving investors an incomplete picture.

The index looks fine.

The average stock doesn't.