The coefficient of variation gives an indication of this. It also shows the extent to which the pound tracks the euro or the dollar. Note the effect of Black Wednesday in late 1992 by comparing the averages for 1992 and for 1993. For consistency and comparison purposes, coefficient of variation is measured on both the "per pound" ratios, although it is conventional to show the forex rates as dollars per pound and pounds per euro. Economy by region The strength of the UK economy varies from country to country and from region to region. Excluding the effects of North Sea oil and gas (which is classified in official statistics as extra-regio), England has the highest gross value added (GVA) and Wales the lowest of the UK's constituent countries. Within England, GVA per capita is highest in London. The following table shows the GVA per capita of the nine statistical regions of England. Trade The trade deficit (goods and services) narrowed £0.2 billion to £7.9 billion in the three months to November 2018 as both goods and services exports each increased £0.1 billion more than their respective imports. Excluding erratic commodities (mainly aircraft) the total trade deficit widened £1.2 billion to £9.5 billion in the three months to November 2018. Large increases in export prices of oil and aircraft drove the narrowing of the total trade deficit; removing the effect of inflation, the total trade deficit widened £0.3 billion to £6.5 billion in the three months to November 2018. The trade in goods deficit widened £0.8 billion with EU countries and narrowed £0.9 billion with non-EU countries in the three months to November 2018, due mainly to increases in imports from EU countries and exports to non-EU countries. The total trade deficit widened £4.1 billion in the 12 months to November 2018 due mainly to a £4.4 billion narrowing in the trade in services surplus. After the withdrawal of the United Kingdom from the European Union, the negotiation of a trade deal between the UK and the European Union including her 27 member states might have the same status than third countries for statistics related to imports and exports with the UK: According to OEC World 2017 data, the EU-27-2020 could become/stay one of the notable partners of the UK, with exports from the UK reaching near $200B, close from the United States ($45B, and China $21B). According to OEC World