摘要：Financial markets struggle with the problem of market abuse behaviors, suchas insider trading and market manipulation. Supervisory authorities that controlthe market should detect and consistently penalize all actions that are illegal interms of local capital market law.Under the name of market manipulation, we comprehend all actions thatlead to security price changes or to a change of perception of market participantson security itself. The actions may be caused by the spread of misleading information(information-based manipulation) or by making transactions (market-basedmanipulation). In each case, the aim of market manipulators is to draw attentionto their operations and to trigger a desired reaction in others. For this reason,market manipulation has a greater chance of being detected than insider trading,which is hidden by insiders. Insider trading relies on making transactions basedon privileged or inside information that is not available to other participants ofthe market. The research on profits from insider trading behavior can be treatedas part of the study on the hypothesis of efficient market formulated by Fama(1970). In its strong form, the hypothesis postulates that even privileged informationis fully reflected in security prices, and that having knowledge of it cannotlead to superior profits. Penalties that are imposed by supervisory authorities forinsider trading do not enforce the strong form of market efficiency. Researchersassume that insider trading leads to unusual security price changes observedahead of an announcement, which has an impact on prices. Increased tradingvolume may be noted simultaneously. Meulbroek (1992) states that this can becaused by uninformed investors who follow insiders and empower the changes in trading. The so-called herd-effect on the Polish stock market is studied by Gurgul and Majdosz (2007).
