The magnificent seven – Apple, Nvidia, Microsoft, Alphabet, Amazon, Meta, and Tesla – have got company, with AI giant Broadcom becoming the latest stock market trillionaire.
Broadcom’s breathless ascent – it soared 40 per cent in December and more than doubled in 2024 – means the eight aforementioned giants have a combined market capitalisation of almost $19 trillion (€18.4 trillion). That’s roughly 35 per cent of the S&P 500′s total value, says Bespoke Investment. Not only is that a record, says Bespoke, it represents a 5.6 percentage point jump for the eight biggest stocks versus last year, one of the largest-ever annual increases in market concentration.
Historically, the norm has been for the eight biggest stocks to come from six different sectors. In contrast, 2025′s big eight are concentrated within just three sectors, each stock exhibiting an AI theme.
“There is no such thing as ‘the US stock market’”, says Acadian Asset Management’s Dr Owen Lamont. Basically, we have two US stock markets – “big growth stocks and everything else”.
Almost 60,000 without power as Met Éireann warns cold spell will continue until Friday
‘My friend was sleeping with another friend’s boyfriend and refuses to take responsibility’
‘I actually felt unsafe as an English person in the Aviva’
I loved Alice Munro but recent revelations have tainted her legacy forever
Why? This “bifurcation” is potentially a symptom of speculative excess, with irrational optimists pushing up big growth stocks and neglecting others. Alternatively, says Lamont, it may not be the stock market that has bifurcated, but the underlying firms, with the market “rationally responding to different fundamentals for different types of firms”.
Whether this is a sign of a bubble or a reflection of a new technological reality will probably be one of 2025′s big investment debates.
- Sign up for push alerts and have the best news, analysis and comment delivered directly to your phone
- Join The Irish Times on WhatsApp and stay up to date
- Listen to our Inside Politics podcast for the best political chat and analysis