(b) Inefficient capital markets: If the market fails to correctly appreciate the
implications of a current earnings surprise in revising its expectations of future
earnings, the price change associated with earnings change will be too small.
There is a large body of evidence that suggests that the stock market underreacts
to earnings information and recognizes the full impact of the earnings
information only gradually over time (see references in Section 3 on the postearnings-
announcement-drift literature and further discussion in this section
under ‘‘tests of market efficiency’’).Sm aller-than-predicted values of earnings
response coefficients are consistent with capital market inefficiency.Su ch an
interpretation, however, should be tempered unless there is a logically consistent
inefficient markets theory that predicts underreaction to earnings information.
The reason is that overreaction is just as easily possible as underreaction in an
inefficient market without a theory that predicts a particular phenomenon.