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what evidence or research suggests that mid- or small-capitalization stocks should perform better than large caps?
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efficient frontier has an article from years ago about the small-cap and value premiums out there that would be worth noting here using the fama and french data. eugene fama and kenneth french (f/f) have shown that one can explain   almost all of the returns of equity portfolios based on only three   factors: market exposure, market capitalization (size), and   price-to-book (value). wikipedia link to the factor model which was the result of the f/f research.
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