Is the Stock Market Efficient?

Andrew ('Mindles Dreck') Hofer provides a nice brief survey of some important alternatives to the efficient markets hypothesis for stock prices.

They make the point that bubbles are created from non-stationary, self-correlated re-pricing of fundamentals, including risk. They describe the reality of markets being perceived as safer because they are going up or riskier because they are going down.

Discussion Question. It is argued that if markets are not efficient, then there are unexploited profit opportunities. Are the profit opportunities implicit in the alternative hypotheses equally exploited?