Good point! But that makes me think that maybe taking the average of a bunch of P&#x2F;E ratios is mathematically stupid to begin with.  I mean, you could have one with earnings of .00000001 which would make the P&#x2F;E ratio enormous, or with earnings of -.0000001 which would make the P&#x2F;E ration enormously negative.  Or you could have earnings of exactly zero which would give you a NaN.  So maybe this is just is an indication that the median P&#x2F;E is a much more meaningful quantity than the average.  Maybe taking the average of a bunch of <i>ratios</i> is meaningless, in general.  Or maybe they are adding up total price of all stocks on the exchange &#x2F; total earnings of all stocks on the exchange.  In that case, you could get the result that the &quot;mean&quot; was much lower than the average, if there were a small number of stocks that were losing bucketloads of money.