I wanted to ask a follow up questions to the questions linked below.
I have a personal financial adviser who follows the diversified portfolio theory, and I've read the explanations in that answer as well as heard of the advantages of a diversified portfolio. However, has anyone put together data that a diversified portfolio of some sort has actually outperformed the S&P 500? I've seen the Blackrock Asset Class returns chart many times and I can see you end up with more stability with the diversified portfolio, but I've never seen anyone cite anything that says such a diversified portfolio actually outperforms the S&P 500 over any time period.
I realize measuring performance can be tricky, as it may depend on which years you choose, or the dates you start your year, but nonetheless, my sense is the diversified portfolio argument is cited as something that's theoretically great, but no one has put together solid data over a long period to show it's better.
EDIT: people have asked for clarification of diversity. By diversity, I mean a portfolio that has holdings from most/all of the assets classes shown in the linked Blackrock chart. I've run into a number of financial advisers who essentially advocate holding as many of those asset classes since you don't know which class will be the best performer.