The wealth effects of mergers on acquirer and target firm shareholders are of interest to a broad
body of academics and practitioners from different fields. Academics are typically interested in
the mechanics of takeover markets, which includes the division of merger-driven wealth between
the merging firms. Mergers and acquisitions (M&A) advisors estimate the wealth effects of past
mergers, especially on the target firm shareholders, to assess whether their clients are receiving
fair premiums from the proposed transactions
The traditional method of estimating the wealth effects of mergers is to perform event studies
around the merger announcement dates. This sort of event study methodology relies on two
assumptions to estimate the wealth effects of mergers: 1) the markets are efficient and 2) the
merger announcement about to be released by the merging firm is unknown to outside investors
at the time of the announcement. Only when these conditions are met does the change in merging
firms’ stock prices accurately reflect the wealth effect of the merger in response to the merger
announcement. The vast majority of the empirical M&A literature relies on these two assumptions
when attempting to identify the factors that shape merger outcomes.
In this paper, we investigate whether the second part of the above-stated premise, merger news
is unknown or unanticipated by outside investors at the time of the announcement, holds around
the primary announcement dates (the “Date Announced” field [DA]) that are recorded in the
Securities Data Corporation (SDC) database, a popular resource used in empirical research.