Source: University of Pennsylvania
Release: Penn World Table 7.1
For more information and proper citation see http://www.rug.nl/research/ggdc/data/pwt/pwt-7.1
Source Indicator: XRAT
University of Pennsylvania, Exchange Rate to U.S. Dollar for United Kingdom [FXRATEGBA618NUPN], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/FXRATEGBA618NUPN, April 24, 2018.