To tackle the second part of the question first, it turns out markets spend rather a lot of the time around their all-time highs. Once you consider that markets generally go up as economies and corporate earnings grow, this shouldn’t come as a huge surprise. Still, it fills many of us with a sense of impending doom when we read these sorts of headlines in the paper.
If we look at the history of US large-cap stocks going back to 1928 (as far as is available on the Bloomberg terminal) we see that in 38% of months the index has been within 5% of its all-time high. If you consider total return, rather than just price, this increases to 51% of the time.
Of course, there have been some bad decades: in the 1930s, the equity market spent precisely zero months within 5% of its all-time high due to the bear market that followed the Wall Street Crash of 1929. Stock prices took until 1932 to trough, eventually falling nearly 90%, and the market didn’t fully recover until 25 years later.
You can say what you want about an AI bubble, but the innovation and earnings growth delivered by these companies has been hugely impressive. Supernormal earnings growth rates can’t go on forever, but the bedrock of the market rally is founded in economic activity rather than pure financial market speculation. This should give us some comfort that it’s not 1929 all over again - even if pockets of the market do look rich - but it is not a reason to be complacent.
All that is a slightly long-winded way of saying that the market being at all-time highs shouldn’t automatically make us nervous because it is very common.