It is good practice to do the static calculation in script or on the data itself if you are using some tool for ETL (e.g. SAS).
Since Qlikview calculates every expression every time when user makes some selection in the report, if we write the expression then QV will be evaluating the expressions every time. But if we do this in the script then QV just needs to pull the values.
But in the above case there is one caveat that if you need to roll up the data and see at some higher level (e.g Market) then doing in script will not help.