1931 Census of England and Wales, General Report, Table 63 : " Percentages of Private Families with Resident Domestic Servants to Total Private Families, England and Wales, Census 1931".

Size of family (persons)* Families with one servant only Families with more than one servant All families with servants
  per cent. per cent. per cent.
2-3 3.0 0.2 3.2
4-5 4.8 1.4 6.2
6 4.8 3.2 8.0
7 3.7 3.6 7.3
8 3.3 3.7 7.0
9 1.3 4.4 5.7
10 1.1 4.8 5.9
11-12 - 10.8 10.8
13 or more - 24.4 24.4
TOTAL 3.7 1.1 4.8

*The size of family is inclusive of the servant(s); e.g. a group of 4 persons employing 2 resident servants is classed as a 6 person family.