-If it was just 2 years, then there must have been quite a disparity for those 2 years. Again, someone investing in this way should be aware of those occasional events and not freak out when they happen.
Your advice seems very sensible, but it's actually backwards and misguided. There was
nothing to freak out about. There was a very rare divergence between the Mids and Large Caps in the last 2 years of the 90's, but both were still going
up during that time. Newbies weren't freaking out and selling either index.
This weird discrepancy in the long(
almost any)-term tight correlation was because the Large Caps bubbled, then popped in the
worst crash any one of us probably ever saw.
So, it was the Large Caps that went bonkers, not the Mids. The 2000's are called the 'lost decade' in investing, but they weren't 'lost' for the Mids -nor were the 90's, 80's, 70's, etc.
I'm claiming now that a Mid Index is straight-up safer/less risky, makes more $, AND doesn't require any special advice other than
exactly the same thing that you'd tell anyone in the Total Market Index.
I think that's the one point we don't agree on. And I could be wrong. I want to be corrected if I am. No one else here advocates for Mids as their core (or only) holding like they do with the Total Market (as far as I've ever seen).
Lack of diversification seems like the strongest argument against a Mid Index (usually ~400 or so companies), but most of us here (including me) consider the Total Market and the 500 Index to be 99% interchangeable, so having WAY less than the thousands of companies in the Total Market obviously isn't an inherent problem.