Right because Berkshire stopped overperforming. In fact it has been underperforming the last 10 years, and Buffet was trying to explain why. https://investorplace.com/2020/10/berkshire-hathaway-stock-u...

But what what I was doing was explaining a counterfactual to show why every firm must stop outperforming. It's not just Berkshire, or 6%, 8%.

So I ran some numbers to explain to you how if A is part of B than the compound growth rare of A cannot forever be greater than the compound growth rate of B.

(Please do not reply to this comment with an argument that you are not talking about any stock called "A" and "B", just as the 6/8 seems to have tripped you up)

Berkshire is part of the market, thus it cannot outperform the market forever. In fact you expect reversion to the mean -- companies that outperform then underperform and vice versa. Why is there reversion to the mean? Because the special techniques discovered by the company are copied and disseminated, key people are poached, ideas that used to work reliably stop working, etc. So these social constraints kick in long before mathematical constraints, but even if in theory you can overcome the social constraints, you can never overcome mathematical constraints, and thus Berkshire and all other investment holding companies must eventually stop overperforming, and most only eek out a few years of net overperformance.