such information will be specific to the firm or possibly its industry. It is
reasonable to expect that there will be ‘active’ times in the stock when such
information arrives and ‘quiet’ times when it does not although the ‘active’ and
‘quiet’ times are random. By its very nature, important information arrives only
at discrete points in time. This component is modeled by a ‘jump’ process
reflecting the non-marginal impact of the information.
To be consistent with the general efficient market hypothesis of Fama (1970)
and Samuelson (1965b), the dynamics of the unanticipated part of the stock