One thing to note, as Simon from Just One Lap realised in one of his podcasts a few months ago, when one of the big Top40 companies start going down and continue its fall into the MidCap index, it drags the whole index down because the smaller companies that make up the MidCap index are too small to negate the negative impact of a larger, previously Top40 company going to hell.
True, but even with the odd company crashing and burning, mid and small cap indexes still outperform large cap in the long term (with more risk of course).
