The first parish register for the chapel of St. Kenelm's dates from 1736-1783, during which time 304 children were baptised. This gives an average of six baptisms per year, suggesting a very low population, but many families may have continued to baptise their children at the parish church in Halesowen. The second parish register dates from 1783-1812 when 167 children were baptised, maintaining the average of six per year. In the third register, the incumbent has helpfully given the fathers' occupations, showing that of the 269 children baptised at St. Kenelm's between 1813 and 1841, 44, or one in six, were sons or daughters of nailers.
Romsley and Hunnington are not treated separately in the national censuses until 1841. In this year the underlining decline in the nail trade in rural areas brought about by the mechanisation of the trade in towns. By 1851, only 42 nailers remained, and half of these were living in poorly-built cottages at Dayhouse Bank. The last nailer in Romsley was John Byng, who maintained a forge near to the Sun Inn until about 1920.
Romsley's agricultural economy was also in decline in the 19th century. Lord Lyttelton's tenants farmed more than half of the village's 900 acres. In 1851 there were only 26 agricultural labours and 21 general labourers. Even the building of a railway through the parish in 1883 provided only a handful of jobs on the line itself. Romsley's numbers remained at about 400 until boosted by 20th century ribbon development and the opening of the Birmingham Hospitals Sanatoritun on Romsley Hill in 1913. The addition to the parish in 1934 of 500 acres at Chapmans Hill and Gannow Green further increased the published population figure. Romsley's population rose from 397 in 1911 to 1,060 by 1951. Council house building more than kept pace with the demolition of older cottages, but the real growth in population came with the building of the new estate between Bromsgrove Road and St. Kenelm's Road, started in 1955. Romsley School, once in danger of closing, was extended and a new row of shops was built opposite the Sun Inn. The census figure in 1961 was 1,572 and further building pushed this up to 1,847 by 1971. Romsley's population was further inflated in the late 1970's by the building of a Birmingham overspill estate near Gannow Green. This raised the official figure for Romsley's population to over 4,000, but recent boundary changes have put these new houses within the city limits and brought Romsley's numbers back to around 2,000.
Hunnington's population began to rise early in the 20th century with ribbon development along Bromsgrove Road. Further growth came with the building of council houses at Red Hill in 1920, Harry Vincent's model village in 1927, and Stewart and Lloyds' houses opposite Oatenfields Farm in 1928. The population rose from 180 in 1901, to 488 by 1951. There has been no significant growth since that date and the 1991 census figure for Hunnington was 517.
The continued growth of Birmingham in the 20th century would have had an even more significant impact on Romsley and Hunnington had the City not pursued a greenbelt policy. Cadbury Brothers set the example by buying land at Lickey and Waseley Hills and set up a trust in 1935 to purchase further greenbelt land which was then transferred to Birmingham Corporation. Goodrest Farm, Hunnington and Dayhouse Farm, Romsley were purchased by the Corporation as part of its greenbelt policy in 1948. The construction of the M5 motorway in the 1960's provided an obvious boundary for the growth of the conurbation and it is now Birmingham Corporation's policy to sell greenbelt land south of the motorway to the sitting tenants.