While it has long been believed that prewar censuses undercounted women's l
abour force participation, a paucity of independent evidence has constraine
d the evaluation of potential biases. This article compares participation r
ates derived from social surveys with censuses for the same towns between 1
911 and 1931. The participation rates for women are uniformly lower in the
social surveys than in the censuses. An analysis of 35 London boroughs indi
cates that some of the discrepancy can be explained by differences in the c
overage of domestic servants, unemployed, own-account, and part-time worker
s. Overall there is little evidence that the census undercounted women's wo
rk.