Do you place your ancestors in context? Perhaps you look at the neighbours to get an idea of their occupations, number of persons in the houses, whether there are lodgers, etc.
That’s not possible for the 1921 Census of England & Wales as now available on FMP — unless you want to spend money ordering the neighbour’s data.
A poor substitute is the Official Reports, now available on FMP, produced in the years after the 1921 Census was taken — statistical reports both regionally and nationally. That’s a broad picture giving statistics on:
Occupations (both male and female)
Movement of population
If you don;t have FMP access these same reports are on HISTPOP starting at http://www.histpop.org/ohpr/servlet/Browse?path=Browse/Census%20(by%20date)/1921&active=yes&treestate=contract&titlepos=0
Also now available on FMP are Occupation Books giving the classification and definition of all occupational terms in the 1921 Census that appear in green ink on the census schedules.