Agree that position sizing is more important than picking. I’ve observed the outcomes of different approaches to investing retirement accounts over 20+ years by some great investors.
First of all, everyone (including ones that beat the index over decades) will make mistakes. Concentration on a few good stocks can make up for the inevitable losers and also for “missing out” on many great ones. A diversified portfolio can perform well but it puts enormous pressure on picking - a few have to perform spectacularly well since a small position will not move the needle until it grows
Either way, the key to superior performance over long periods is inactivity. Must let it compound. Hard to keep up otherwise. I’d say impossible, if the accounts are taxable.
Over time, even diversified portfolios, if performing well, start to look concentrated.
Buffett’s view is you don’t get many great opportunities in a lifetime of investing. When you come across one of the rare ones, doing too little is almost as bad as not doing it as all (and the job of the investor is to develop the judgement to be able to recognize such opportunities).
