An @ONS interactive graphic - Population increased in #1961 #rural districts - Explore 1961 area population size compared with #2011 (1961 boundaries)

Text from source post "the cities of Birmingham, Manchester, Leeds, Liverpool, Sheffield and Bristol - Of those six urban centres, five also saw the biggest reductions in the proportion of the population of England and Wales they were home to between censuses. The city of Birmingham, as it was defined in 1961, went from housing 2.4% of the population to 1.7%. Places that saw an increase in population proportion between censuses were generally areas that in 1961 were classed as rural districts. As cities spread, people moved and the New Towns were built, some of these previously rural districts became more urbanised." Source = this @ONS post