In my 401k I have always allocated a greater percentage of my portfolio into mid cap funds because they seem to be riskier and have a higher upside. Yet, as of the past year or so, the large cap funds are beating them.
Is there any research or trains of thought that says what is more likely to do what over 30 years between a mid-cap fund based on, say, the Russell 2000 vs. a large-cap fund based on, say, the S&P 500?
I was looking at this Morningstar brochure "The Perfect Mix of Large-, Mid-, and Small-Cap Stocks" (PDF), but is that always the case? Like over 30 years, should mid cap and small caps constantly beat the S&P 500?