Sometimes a chart just makes you stop what you're doing and gawp. Alphaville came across one such chart today in a new note from Goldman Sachs's Christian Mueller-Glissmann, ostensibly about reassessing the value of holding bonds in a balanced portfolio. It shows the proportion of S&P 500 stocks with a negative beta: In layperson's terms, a stock with negative beta is one that zags when the market zigs. One that does, on average, precisely the opposite of what you'd think a stock might do given what's going on in the rest of the market. So sure, it'll always be the case that some stocks do well and others do poorly. But beneath any exceptional stock-specific performance on any one day, stocks are mostly just zigging with the herd, though maybe faster or slower than the rest. Goldman's chart suggests that almost half of US large-cap stocks are now zaggers. Beyond noting that "the proportion of stocks with a negative beta to the market has increased sharply, very similar to the Tech Bubble", Mueller-Glissmann doesn't have anything else to say about it, at least in this note.

Of course, it's all about tech and index concentration. Back in June, FTAV picked up the theme in our weekly Substack: To those looking for a ray of sunshine, one spin could be that — despite the big AI trade accounting for half of US economic growth, staggering amounts of equity market cap, much of private credit, a growing slug of public credit, as well as a ton of infrastructure and real estate — there could be plenty of diversification trades out there. Good news, relatively, for portfolio managers restricted to the US stock market but nervous that the whole thing comes tumbling down.