What's going on?

The US stock market hit another record high on Thursday, but there are signs that all this good fortune is about to run out.

What does this mean?

A slump wouldn�t be totally unprecedented: research firm CFRA has pointed out that the S&P 500 has delivered a positive return in September less than half the time since World War 2. In fact, the key US stock market index has actually fallen by an average of 0.56%. Plus, there�s added pressure from the Delta variant this year, whose spread � and all the knock-on economic effects it brings � could accelerate with a return to school. That�s on top of the slowdowns some retailers and restaurants are already reporting.

Then there�s the little matter of the US central bank: the Federal Reserve is expected to include details of when it�ll reduce support for the US economy at its update later this month. And even if it doesn�t start rolling back its bond-buying program for some time, stock prices are bound to fall long before it takes any action.

Why should I care?

The bigger picture: Brace yourself.

Economists seem to know what�s coming: they�ve cut their average third-quarter US economic growth forecasts to 6.2%, down from 6.9% a few months ago. And here�s another warning sign besides the numbers: investment management giant Fidelity is planning to hire 9,000 people to handle the high demand for stocks from retail investors, and finance firms have a history of hiring surges right before a big crash.

For you personally: Demand might already have disappeared.

CMC Markets announced on Thursday that it had been seeing lower-than-expected trading activity. The retail trading platform � which partly put its disappointing update down to the loss of investor interest as they ventured out of their homes � said it�s expecting its annual profit to be as much as 25% lower than investors were expecting, and its shares fell 28%.