Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

What evidence exists for claiming that you cannot beat the market?
Will the investor beat the benchmark for a given period will follow a Bernoulli distribution -- each period is a coin toss, and heads mean the investor beat the market for that period.   I can't prove the negative that there is no investor ever whose probability function p = 1, but you can statistically expect a number of individual investors with p ~ 0.5 to have a sequence of many heads in a row, as a function of the total population.   By example, my father explained investment scams and hot-hand theory to me this way when I was younger:  Imagine an investor newsletter which mails out to a mailing list of 1024 prospects (or alternately, a field of 1024 amateur investor bloggers in a challenge).  Half the letters or bloggers state AAPL will go up this week, half that AAPL will go down this week.  In the newsletter case, next week ignore the people we got wrong.  In the blogger case, they're losers, so we don't pay attention to them.  Next week, similar split: half newsletters or bloggers claim GOOG go up, half GOOG go down.  This continues for a 10 week cycle.   Now, in week 10: the newsletter has a prospect they have hit correct 10x in a row: how much will he pay for a subscription?  Or, one amateur investor blogger has been on a 10 week winning streak and wins the challenge, so of course let's give her a CNBC show after Jim Cramer.  No matter what, next week, this newsletter or investor is shooting 50-50.   How do you know this person is not the statistically expected instance backed up by a pyramid of 1023 Bernoulli distribution losers?  Alternately, if you think you're going to be the winner, you've got a 1/1024 shot.