On summer days, the inherently repetitive nature of my hobby-job feels more oppressive than it does when it isn’t hot outside.

I don’t know why that is. It’s not hot inside. Whatever the reason, I like to foist my frustration onto readers. Misery, as they say, loves company.

The saving grace (for you) is that even my contemptuous pieces are at least marginally educative, if not wholly edifying.

Even when I’m deriding “Mr. Market” as a drab fellow whose pretensions to intrigue are indistinguishable from vacuous appeals to the basest of human instincts (namely greed), I always build around some kernel of useful information. To quote history’s second-greatest ad man (the first being Don Draper), I find anchors that “are funny or mildly amusing or interesting.”

With that in mind, consider the figures below, from SocGen’s Andrew Lapthorne. The chart on the left’s more than “interesting.” It’s incredible: The 20 largest stocks in the MSCI All-Country World universe are, on average, sixty times bigger than the average of the other 2,500 stocks in the index. In the decade from 2007 to 2017, that multiplier was between 20 and 25.

The figure on the right just shows you the extent to which breadth has collapsed across cap-weighted indexes in both the developed and emerging worlds.

As Lapthorne noted, “Concentration risk is not going away any time soon and with a list of ultra-caps now coming to the market, the problem is likely to get worse.” (SpaceX enters the Nasdaq 100 this week, albeit with a low initial weight.)

Why is this a problem? Let me (and Andy) count the reasons. Viewed through a portfolio management lens, the issue “is that benchmark risk forces many institutional investors to take positions in stocks they do not even like,” Lapthorne wrote. “Being on the wrong side when [the biggest stocks] move up is painful, so you hold them, simply to keep up with the benchmark.”

And what does that mean? Well, coming full circle, it means Mr. Market’s becoming less interesting all the time. As more and more funds pile into the same ultra-caps to avoid underperforming, more and more funds begin to look like the index. So, as Lapthorne wondered, “Why not just buy the index?”

It was a rhetorical question. He answered it anyway: That’s “essentially what investors have been doing.”