United States. Bureau of Economic Analysis. "U.S. International Trade in Goods and Services: December 2018 : Highlights, Annual: 2018 Trade Gap is $621.0 Billion, BEA 19-07, CB 19-15," Bureau of Economic Analysis (BEA) News Releases (March 6, 2019). https://fraser.stlouisfed.org/title/6148/item/602780/content/pdf/bea_newsreleases_20190306_release-highlights-annual, accessed on March 15, 2025.