This paper shows that the systematic risk (or 'beta') of individual stocks increases by an economically and statistically significant amount on days of firm-specific news announcements, and reverts to its average level two to five days later. We employ intra-daily data and recent advances in...

We investigate whether the betas of individual stocks vary with the release of firm-specific news. Using daily firm-level betas estimated from intra-day prices for all constituents of the Samp;P 500 index, we find that the betas of individual stocks increase by an economically and statistically...