Extending the literature that has focused thus far on stock price impact, this study investigates the effect of data breach announcements on market activity, specifically through the response of the bid-ask spread and trading volume. We investigate data breach announcements as a potential source of asymmetric information and provide a new dimension to the ongoing debate on market efficiency. Adopting an event study methodology on a sample of 74 data breaches from 2005 to 2014, we find that data breach announcements have a positive short-term effect on both bid-ask spread and trading volume. The effect is only evidenced however on the day of the event, with market efficiency ensuring a quick return to normal market activity. No abnormal trading activity emerges before announcements, so there is no evidence in our study that these types of events are being exploited by informed market participants. The magnitude of event day effects is found to be more pronounced for large breaches, and when the breach involves lost devices.

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Data breaches are not only on the increase but firms struggle to detect, defend and respond to such breaches. A data breach opens a period of crisis for the affected firm, generates complex information, and requires providing information to a variety of stakeholders in a timely and proper manner. This article reports one of the first studies on the impact of social media exposure by affected firms on stock price reaction to a data breach announcement. Using an event study methodology on a sample of 87 data breaches from 73 US publicly-traded firms from 2011 to 2014, we find that use of social media exposure at the time of a data breach exacerbates the negative stock price to the announcement. Interestingly, we find that this negative association is contingent on traditional media visibility; the effect is positive for low-visibility companies. Based on our results, we posit that there is a need for a contingency model for social media communication during firm crises and such a model should be based at least on firm size, visibility and the type of crisis.

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Data breaches represent one of the main concerns for executives across all sectors. Data breaches open aperiod of crisis for the affected firm and require them to disclose complex information to a variety of stakeholders in a timely and proper manner. This paper investigates the relationship between social media disclosure of a data breach and its cost, as proxied by the response of the affected firm's stock price. Using an event study methodology on a sample of 32 data breaches from 29 US publicly-traded firms from 2011 to 2014, we find that social media disclosure exacerbates the negative stock price's response to the announcement. However, such a negative association is contingent on firm's visibility on traditional media with social media disclosure having a beneficial effect for low-visibility companies.

The decisions of the European Parliament (EP) are shown to in uence both EU emission allowance (EUA) prices and volatility. Reductions in price and increases in volatility are observed when EP decisions are (i) not partypolitical in origin, (ii) made during times of low market sentiment, or (iii) made during times of low market attention. Daily EUA prices from 2007 to 2014 are used in the study, with decisions analysed using an event study approach for price impact, and a GARCH speci cation for volatility impact.Our ndings suggest the need for policymakers to improve communication of long-term strategies for the EUA market. This aims to reduce the evident ongoing uncertainty experienced by traders around each decision made by the EP. The nding that sentiment and market attention at the time of an EP decision in uences the market's reaction indicates a need to consider market dynamics in terms of decision timing, so that market turbulence is not an unintended by-product of an EP decision. Indeed some form of medium term forward guidance may be called for.JEL: Q58, G14, C12

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