United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services, December 2020 : Highlights (Annual): 2020 Trade Gap is $678.7 Billion, BEA 21-04, CB 21-17," Bureau of Economic Analysis (BEA) News Releases (February 5, 2021). https://fraser.stlouisfed.org/title/6148/item/600388/content/pdf/bea_newsreleases_20210205_highlights-annual, accessed on March 21, 2025.