We decided to release, in June 2003, a version 0.8a1 (May 2002) of

We decided to release, in June 2003, a version 0.8a1 (May 2002) of
former version 0.8a to correct a bug highlighted by Chris Jackson.
It can be useful until version 0.9x will be released.

In version 0.8a, likelihood was computed as if date of death was unknown. Death
was treated as any other health state, i.e the date of the interview
describes the actual state and not the date of a change in health
state.

It means that in the early version of IMaCh we were considering that
at each interview the current state was recorded (healthy, disable or
death).  And IMaCh was correct. But, when we introduced the exact date
of death then we should have modified the contribution of an exact
(more precise) date of death to the likelihood. This new contribution
is smaller and very dependent of the step unit stepm. It is no more
the probability to die between last interview and month of death
(which is the way version 0.8a of IMaCh was doing) but the probability
to survive from last interview up to one month before death multiplied
by the probability to die within a month. Thanks to Chris Jackson for
correcting this bug.  Former versions increased mortality
artificially. The bad side is that we add another loop which slows
down the processing. The difference can be up to 10% lower mortality.