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Is diversification better
There are probably 3-4 questions here.  Diversification - A good index, a low cost S&P fund or ETF can serve you very well. If you add an extended market index or just go with "Total market", that might be it for your stock allocation. I've seen people with 5 funds, and it didn't take much analysis to see the overlap was so significant, that the extra 4 funds added little, and 2 of the 5 would have been it. If you diversify by buying more ETFs or funds, be sure to see what they contain.  If you can go back in time, buy Apple, Google, Amazon, etc, and don't sell them. Individual stocks are fun to pick, but unless you put in your homework, are tough to succeed at. You need to be right at the buy side, and again to know if, and when, to sell. I bought Apple, for example, long ago, pre-last few splits. But, using responsible a approach, I sold a bit each time it doubled. Has I kept it all through the splits, I'd have $1M+ instead of the current $200K or so of stock. Can you tell which companies now have that kind of potential for the future?  The S&P has been just about double digit over 60 years. The average managed fund will lag the S&P over time, many will be combined with other funds or just close. Even with huge survivor bias, managed funds can't beat the index over time, on average. Aside from a small portion of stocks I've picked, I'm happy to get S&P less .02% in my 401(k). In aggregate, people actually do far worse due to horrific timing and some odd thing, called emotions.