Info ormation arrivals and price updates The efficient market theory states that security prices reflect all currently available information One interesting empirical question is: how does the market adjust to the arrival of new information Event study methodology is one such tool to measure the economic impact of eventsInformation arrivals and price updates • The efficient market theory states that security prices reflect all currently available information. • One interesting empirical question is : how does the market adjust to the arrival of new information? • Event study methodology is one such tool to measure the economic impact of events