https://www.reddit.com/r/Bogleheads/comments/ikc6n0/so_you_want_to_buy_us_large_cap_tech_growth/

I bet you're wondering how we got here .... Imagine this: the year is 2010, and you're about to start investing, but not sure how. Let's compare Total Stock, Total International, Emerging Markets and a Growth Index. Feel free to look up the tickers, but that one way at the bottom? Yes, that's US large growth. Uh oh. At the time, it seemed obvious that the smart money was on small caps, value and emerging markets -- anything but US and/or large and/or growth.

In hindsight, 2010 turned out to be the start of a great decade for everything that had done badly in the 2000s. A tilt toward small, value, emerging (that had been doing well) all had substantially poorer returns in the 2010s. And then there's tech, the current darling: if we add that to the 2000s chart and see how QQQ did, well, it's at the very bottom. After 10 years it had -55% returns. Ouch. People who were diversified globally, however, did fine both decades.

Point being: if you'd used 2000s results to craft a 2010s portfolio, you'd have done horribly. You certainly wouldn't have tilted toward US growth or tech - you might have left some of that out entirely. And yet here we are, with new people daily asking about tilting toward US large and tech for the 2020s based on the 2010s. I don't know what will do well next. But we do know from prior decades that chasing recent winners can wind up yielding terrible results.

I ask you to ask yourself: if you tilt toward US/L/G/Tech and it fails for ten years, what will you do? Really think on that. At the end of the day: your investments, your money, your call. I'm just trying to help people avoid mistakes I made, pay it forward to the next generation (in gratitude to those who helped me many years ago). Not sure where to start? Consider a Target Date retirement fund or a baseline of Vanguard Total World + Total Bond. Good luck.

Update 1: In the three months since I posted this, US large cap growth is up 10% while US small cap value is up two and a half times as much (25%). In fact, small, value and emerging are all ahead of US large, growth and tech. I mention this not to recommend chasing these recent winners, but as a reminder that winners rotate.

Update 2: It's now been six months and the spread is even larger. US large caps are up 12% while US small cap value is up 40%. Emerging and developed international each continue to be ahead of US -- winners rotate.

P.S. I'm not advising anyone to play the contrarian and buy what isn't doing well, but I am advising against tilting toward what has done well recently, because (and I can't type this enough) winners rotate. If you want to understand how to invest like a Boglehead, remember that the keys are diversification and staying the course.

P.P.S. Just to head off a common counter-argument from performance-chasers: yes, in theory, if you had bought QQQ and held it while it dropped nearly 80%, then kept investing for 20 years, you'd eventually have come out ahead. Unfortunately, while that sounds simple in hindsight, most investors bail when their stocks drop that far that fast. Notably, too, people are not talking about buying QQQ at a discount right now - rather, it's highest point ever.

P.P.P.S. Some folks are questioning the starting and end points of graphs. I picked the dates I did because it was easy to look at two back-to-back decades, plus it illustrates winners rotating. If you're dead-set on learning the hard way by riding the rising tide of what's hot now, do what you have to. But there are ways to learn without banking your hard-earned savings on it, and some of those are right there in the sidebar, or among your peers' responses.

P.P.P.P.S. So you're still not convinced - you see those sweet, juicy, tantalizing returns of QQQ or growth or whatever and it's hard to resist. It's natural. The key is to cultivate an attitude of buying low and selling high, diversifying and staying the course. Yes, it's less exciting than gambling, but this is your future, not a poker hand. If you're someone who still needs to learn through losses, so be it - I just hope you learn while the financial stakes are still low for you.

P.P.P.P.P.S. 'But Bogle and Buffett are all about the US large cap 500 index!' Well, here's my response to that FWIW