1931 Census of England and Wales, General Report, Table 23 : " Population and Electorate (Excluding Universities), England and Wales, 1921 and 1931".

  Census of 1921 Census of 1931
Total Males Females Total Males Females
Population 37,886,699 18,075,239 19,811,460 39,952,377 19,133,010 20,819,367
Electorate 17,758,700 10,206,277 7,552,423 26,048,834 12,221,087 13,827,747
Persons of franchise age* 20,251,563 10,754,022 9,497,541 26,309,890 12,277,504 14,032,386
             
Average for each of the 520 Parliamentary Representatives (excluding Universities)
             
Population 72,859 34,760 38,099 76,831 36,794 40,037
Electorate 34,151 19,627 14,524 50,094 23,502 26,592
Persons of franchise age* 38,945 20,681 18,264 50,596 23,611 26,985

*21 and over for males in both 1921 and 1931; 30 and over for females in 1921 and 21 and over in 1931.