In any event, at those entities with significant merchant banking portfolios, the above average variance in stock prices will doubtless add to the variability of earnings of the overall organization - and hence, one can conclude, to the organization’s valuation in the marketplace.
There is, indeed, general agreement that the price-earnings ratio of trading banks is lower than that of other banks of the same size, although it has been difficult because of the dynamics of other variables to nail down empirically the appropriate orders of magnitude.