with many often quirky independent businesses. The UK-based Tesco is the fourth-largest retailer in Europe measured by turnover (after Swartz, Aldi, and Carrefour in 2019). Currency London is the world capital for foreign exchange trading, with a global market share of 43.1% in 2019 of the daily $6.6 trillion global turnover. The highest daily volume, counted in trillions of dollars US, is reached when New York enters the trade. The currency of the UK is the pound sterling, represented by the symbol "£'. The Bank of England is the central bank, responsible for issuing currency. Banks in Scotland and Northern Ireland retain the right to issue their own notes, subject to retaining enough Bank of England notes in reserve to cover the issue. The pound sterling is also used as a reserve currency by other governments and institutions, and is the third-largest after the US dollar and the euro. The UK chose not to join the euro at the currency's launch. The government of former Prime Minister Tony Blair had pledged to hold a referendum to decide on membership should "five economic tests" be met. Until relatively recently there was debate over whether or not the UK should abolish its currency and adopt the euro. In 2007 the Prime Minister, Gordon Brown, pledged to hold a public referendum based on certain tests he set as Chancellor of the Exchequer. When assessing the tests, Brown concluded that while the decision was close, the United Kingdom should not yet join the euro. He ruled out membership for the foreseeable future, saying that the decision not to join had been right for the UK and for Europe. In particular, he cited fluctuations in house prices as a barrier to immediate entry. Public opinion polls have shown that a majority of Britons have been opposed to joining the single currency for some considerable time, and this position has hardened further in the last few years. In 2005, more than half (55%) of the UK were against adopting the currency, while 30% were in favour. The possibility of joining the euro has become a non-issue since the referendum decision to withdraw from the European Union in 2016 and subsequent withdrawal in 2020. Exchange rates Average for each year, in USD (US dollar) and EUR (euro) per GBP; and inversely: GBP per USD and EUR. (Synthetic Euro XEU before 1999). These averages conceal wide intra-year spreads.