The impact of ECB macro-announcements on bid–ask spreads of European blue chips

• Transaction costs on stock markets rise during important ECB announcements.
• Effects on spreads are strong and transitory.
• Information surprises and uncertainty lead to higher spreads.

Bid–ask spreads using intraday data reveal significant sensitivity to European Central Bank (ECB) macro-announcements. Effects are strongest for announcements that comprise unexpected information or a change in interest rates, and spreads rise sharply during the minutes surrounding interest rate or other important macroeconomic announcements by the ECB. Both Euro area stocks (of German DAX 30 and French CAC 40) and non-Euro area stocks (of FTSE 100) have been used for comparative reasons. All results are robust to changes in specification and when being controlled for normal daytime-dependent frictions and stock-specific characteristics.