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the range was smaller ; thus the rates in 1950-52 ranged from 19 to 31 in the 28 London
boroughs, from 29 to 47 in the seventeen county boroughs of Lancashire, and from
23 to 38 in the eleven county boroughs of Yorkshire West Riding. The low level and
relatively small range of infant mortality make the London boroughs unrepresentative
of urban areas in general. Use of the 1931 census data showed that, although the infant
mortality by social class in London showed the same progression as in the whole of
the country, the usual indices of social structure in urban areas were less highly correlated
with infant mortality than formerly. It was reasonable to suppose that these correlations
would have declined still further during recent years, although the social class differential
would still exist. No data, however, existed to test this hypothesis until the publication
of the 1951 census for London. The occupational supplement is not yet published and
it is not possible to display the infant mortality by social class, but there is no reason to
suppose that the relative differences between the social classes has undergone much
change. A triennial period centred in the census year was used for the appropriate rates
shown in Table VIII, overleaf.
For the County of London as a whole, infant mortality in 1950-52 (24 per 1,000)
was less than one-quarter of the rate in 1911-13 (109 per 1,000). The largest falls occurred

in boroughs where the rate was previously very high, the ratio of the lowest to the
highest infant mortality being 2.1 in 1911-13 and 1.6 in 1950-52. The correlations
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