The economy of the United Kingdom is a highly developed social market and market-orientated economy. It is the sixth-largest national economy in the world measured by nominal gross domestic product (GDP), ninth-largest by purchasing power parity (PPP), and twenty second-highest by GDP per capita, constituting 3.3% of nominal world GDP. By PPP (purchasing power parity) terms, UK constitutes 2.34% of world GDP. The United Kingdom is one of the most globalised economies, and comprises England, Scotland, Wales and Northern Ireland. In 2020, the UK was the fifth largest exporter in the world and the fifth-largest importer. It also had the third-largest inward foreign direct investment, and the fifth-largest outward foreign direct investment. In 2020, the UK's trade with the 27 member states of the European Union accounted for 49% of the country's exports and 52% of its imports. The service sector dominates, contributing 81% of GDP; the financial services industry is particularly important, and London is the second-largest financial centre in the world. Edinburgh was ranked 17th in the world, and 6th in Europe for its financial services industry in 2021. The UK technology sector is valued at US$1 trillion, third behind the United States and China. 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 the largest city by GDP per capita in Europe. In the 18th century, Britain was the first nation to industrialise. During the 19th century, through its expansive colonial empire and technological superiority, Britain had a preeminent role in the global economy, accounting for 9.1% of the world's GDP in 1870. 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, leading into the 20th century. The cost of fighting both the First and Second World Wars further weakened the UK's relative position. Despite a relative decline in its global dominance, in