- now tells you which variables you asked for are not in particular
years, they will show up as missing values in the final pooled file

due to:
- variables in upper case after 2009 (why?)
- mis-matching variable types in different years (why?)

This made it complicated to use a core set of variables and match year
by year.

only keeps a basic core of variables to produce a smaller file on the
assumption that this will be linked back to source expenditure data for
specific analyses

harmonises EFS/LCFS from 2001/2 to 2010 (currently) to form a micro
data time series. Not all variables are included.