<P> The economy of the United Kingdom is a highly developed market - oriented economy . It is the fifth - largest national economy in the world measured by nominal gross domestic product (GDP), ninth - largest measured by purchasing power parity (PPP), and nineteenth - largest measured by GDP per capita, comprising 3.9% of world GDP . It is the second - largest economy in the European Union by both metrics . </P> <P> In 2016, the UK was the tenth - largest goods exporter in the world and the fifth - largest goods importer . It also had the second - largest inward foreign direct investment, and the third - largest outward foreign direct investment . The UK is one of the most globalised economies, and it is composed of (in descending order of size) the economies of England, Scotland, Wales and Northern Ireland . </P> <P> The service sector dominates the UK economy, contributing around 80% of GDP; the financial services industry is particularly important, and London is the world's largest financial centre . Britain's aerospace industry is the second - largest national aerospace industry . Its pharmaceutical industry, the tenth - largest in the world, plays an important role in the economy . Of the world's 500 largest companies, 26 are headquartered in the UK . The economy is boosted by North Sea oil and gas production; its reserves were estimated at 2.8 billion barrels in 2016, although it has been a net importer of oil since 2005 . There are significant regional variations in prosperity, with South East England and North East Scotland being the richest areas per capita . The size of London's economy makes it one of the largest cities by GDP in Europe . </P> <P> In the 18th century the UK was the first country to industrialise, and during the 19th century it had a dominant role in the global economy, accounting for 9.1% of the world's GDP in 1970 . From the late 19th century the Second Industrial Revolution was also taking place rapidly in the United States and the German Empire; this presented an increasing economic challenge for the UK . The costs of fighting World War I and World War II further weakened the UK's relative position . In the 21st century, however, it remains a global power and has an influential role in the world economy . </P>

What is the uk's biggest industry today