The market portfolio is no longer efficient due to the systematic behavior of uninformed investors or savvy trading strategies. Do you believe there exists an efficient market portfolio? All the biases in this chapter explain the relationship between market efficiency and portfolio, but it presumes that there exists a market portfolio, and we can measure the efficient level of it. What do you think of this argument? What is your stance on the on-going debate? Do you agree or disagree, and why or why not?