You would have to change the format definition.  It currently looks like this:   Proc format; VALUE $ZIPFMT ' 48021'='InCounty'                               OTHER='OutCounty' ;   You would need to add a  category:   Proc format; VALUE $ZIPFMT ' 48021'='InCounty'                               ' ' = 'Missing'                               OTHER='OutCounty' ;   Make sure that OTHER= gets defined last. ... View more