According to the 2011 census, the total population of the United Kingdom was around 63,182,000. It is the 22nd-largest in the world. Its overall population density is 259 people per square kilometre (671 people per sq mi), with England having a significantly higher population density than Wales, Scotland and Northern Ireland. Almost one-third of the population lives in England's southeast, which is predominantly urban and suburban, with about 8 million in the capital city of London, the population density of which is just over 5,200 per square kilometre (13,468 per sq mi).
The population of the United Kingdom is considered an example of a population that has undergone the 'demographic transition' – that is, the transition from a (typically) pre-industrial population with high birth and mortality rates and only slow population growth, through a stage of falling mortality and faster rates of population growth, to a stage of low birth and mortality rates with, again, lower rates of population growth. This population growth through 'natural change' has been accompanied in the past two decades by growth through net international migration into the UK.
The United Kingdom's assumed high literacy rate (99% at age 15 and above) is attributable to universal public education introduced for the primary level in 1870 (Scotland 1872, free 1890) and secondary level in 1900. Parents are obliged to have their children educated from the ages of 5 to 18 (raised from 16 in 2013), and can continue education free of charge in the form of A-Levels, vocational training or apprenticeship to age 18. About 40% of British students go on to post-secondary education (18+). The Church of England and the Church of Scotland function as the national churches in their respective countries, but all the major religions found in the world are represented in the United Kingdom.
The UK's population is predominantly White British. Being located close to continental Europe, the countries that formed the United Kingdom were subject to many invasions and migrations from the continent, especially from Scandinavia, including Roman occupation for several centuries. Historically, British people were thought to be descended mainly from the different ethnic stocks that settled there before the 11th century: pre-Celtic, Celtic, Anglo-Saxon, Viking and Norman. Although Celtic languages are partially spoken in Scotland, Cornwall, and Northern Ireland, the predominant language overall is English. In North and West Wales, Welsh is widely spoken as a first language, but much less so in the South East of the country, where English is the predominant language.