Tomasz Potocki | Tomasz Świst
  Abstract: Our study examines the present status and the attacks on the semi-strong efficient-market hypothesis as well as the relationship between predictability and efficiency. We conclude that our Polish stock market is more efficient and less predictable than many recent academic papers would have us believe. In addition, we measure the level of market efficiency on the Warsaw Stock Exchange and describe its implications. We find that proofs from behavioral finance help us to understand the EMH. The future challenge for economists is to make behavioral reality a better part of their models. We conclude that stock markets are efficient because they stop investors from getting above-average returns (in a general way). Markets might also be efficient even if active market players are irrational or when stock prices show unpredictability greater than that which may be explained by fundamentals such as earnings and dividends.