Does leverage have any to do with this? If we take a look at the growth rate of earnings of mid/small caps vs large caps we will probably find that small and mid caps tend to have greater growth rates and therefore you would expect greater growth rates from them. Still we don't see that and maybe it is because larger companies have access to cheaper and bigger access to debt, which then in turn would enhance their equity return, and I think that is someting that exacerbated after the last financial crisis and the subsequent overregulations in the bank's balance sheets that made debt more restrictive to small and mid cap companies.