The second group of variables are Imputed Variables. In the Voyages Database interface, users can choose 22
of these imputed variables to facilitate searches. The imputed variables are derived directly from the data set. The assumptions
underlying these derivations are explained more fully below, but mostly the derived variables are amalgamations or
regroupings of the historical data from the first group of variables. To make the imputed variables as transparent as possible
and to facilitate refinements, alternative assessments, and corrections that users might think necessary, we have included a
download page which makes the database available to users in various formats. Indeed, it provides users with the data needed to create
their own imputed variables.