than Inner London. By the end of the 20th century this figure was 80% of the country. However importance of the capital declined, by the end of the 20th century, London's ranking on the most populated cities of the world had fell down to not even being in the top 20. The current classification of an 'urban' area, also termed as a 'built-up area' (BUA) in the 2011 census, is a settlement which takes variables from both numerical population numbers and population density; in population numbers this is roughly more than or 10,000 people living in a area. Anything below that is classified as 'rural', having several levels of distinction to define a rural town and fringe, village or hamlet which is usually taken from population density figures. These areas are then defined within 'output areas' (OA's) themselves, which are geographic areas of the United Kingdom. The population which resides within classified 'urban' areas was 84.4% of total population in 2022 and the annual rate of urbanisation change is estimated to be around 0.8% between 2020 and 2025. Vital statistics (1900–2022) Current vital statistics Social issues Marriage, divorce, families and household types Marriage and divorce In 2004, 58% of births were conceived within a married couple, 35% by non-married couples registered by both parents and 7% by non-married mothers who registered the birth alone. This varied from each constituent nation, Wales for example had the highest births outside of marriage at 51% in 2004, In England this percentage was 42% and in Scotland 47%. Northern Ireland had the lowest of 35% in 2004. Household and family type Sexual orientation The Integrated Household Survey, published by the Office for National Statistics, provides the following estimates for the adult British population as of 2011: 1.1 per cent (approximately 545,000 adults at the time of the survey) identify as gay or lesbian. 0.4 per cent (approximately 220,000 adults) identify as bisexual. 0.3 per cent identify as "other". 3.6 per cent of those surveyed replied "don't know" or refused to answer the question. 0.6 per cent of those surveyed provided "no response" to the question. An estimated 2.7 per cent of 16-year-olds to 24-year-olds in the UK identify as gay, lesbian or bisexual compared with 0.4 per cent of those aged over 65. Other sources provide alternative estimates of the population by sexual orientation. For example, one British journal published in 2004 estimated that