Big Tech is driving big swings in the stock market. 

Investors this past week finally got a look at earnings from some megacap technology companies—and their artificial-intelligence spending spree—and found a mixed bag.

Upbeat results from Amazon.com helped power the Nasdaq composite to a seventh straight monthly gain on Friday, its longest such streak since 2018. That came a day after investors punished Microsoft and Meta Platforms for their spending plans, with Meta losing $215 billion of market value in a single session.

The rapid growth, high valuations and outsize influence of major AI players have some on Wall Street worrying about a tech-fueled bubble akin to the dot-com boom and bust.

Here’s a look at what investors learned from the reports:

Rising investment

Leading tech companies have already poured hundreds of billions of dollars into their AI efforts—but that bill is only going to get bigger next year. This past week, Meta, Alphabet, Microsoft and Amazon all told investors that they will increase spending in 2026.

The concern among some investors is that it is unclear how, and when, all that investment will start to pay off. The size of the boom implies that a massive shift in the economy would be needed to make current spending worthwhile.

Rising profits

There’s one key difference between the AI players of today and the dot-com names of two decades ago: The leaders of this market are making plenty of money. Both Meta and Alphabet reported record revenues this past week.

But all the AI spending is starting to take a toll: The 12-month cumulative cash flow for Meta, Alphabet, Microsoft, Apple and Amazon has dropped in the past couple of years.

Surging values

As the AI frenzy ratchets up, a few of the market’s tech titans have notched record-setting valuations.

On Wednesday, Nvidia became the first company to hit $5 trillion in market value. Shares gained 8.7% over the course of the week, boosted by upbeat remarks from Chief Executive Jensen Huang at an event in Washington, D.C.

It wasn’t the only tech giant to reach a milestone this past week: Apple and Microsoft each closed above $4 trillion in market cap for the first time on record.

Growing influence

The so-called Magnificent Seven stocks—Apple, Alphabet, Amazon, Meta, Microsoft, Nvidia and Tesla—have never been more influential to the overall market. The group’s market capitalization now accounts for roughly 38% of the entire S&P 500 index, according to Dow Jones Market Data.

That means a move in just one can shift indexes. Nvidia’s market cap, for example, is larger than some entire sectors of the S&P 500, including utilities and consumer staples.

Mounting debt

Once known for holding giant piles of cash and relatively little debt, tech giants have changed in recent years. While they still hold plenty of cash, they have added debt to fund share buybacks, and more recently have started borrowing heavily to fund their AI investments. 

Recently, Meta issued $30 billion of bonds to fund “general corporate purposes” generally understood to mean AI spending. That came about a month after Oracle issued $18 billion of bonds, while it spends big on AI infrastructure.