Some areas of Bicester have changed very little - for example King's End and Market Square - whereas parts of Sheep Street and North Street are almost unrecognisable. Nearly 80 per cent of the buildings in Market Square and the Causeway are classified as 'buildings of interest' under the English Heritage Listed Buildings scheme and this has given them an element of protection from development. Bicester was, and still is, predominantly a market town serving the needs of not just those who lived in the town but also those from the surrounding villages. Its population remained static at around 3,000 for the hundred years preceding 1920. By 1951 it had only risen to just over 4,000 but, over the last 30 years, this figure has risen to over 30,000 and Bicester has seen a period of considerable growth and development.