United States. Bureau of Economic Analysis. "Gross Domestic Product, Fourth Quarter and Year 2021 (Second Estimate) : Technical Note, BEA 22-05," Bureau of Economic Analysis (BEA) News Releases (February 24, 2022). https://fraser.stlouisfed.org/title/6148/item/611516/content/pdf/bea_newsreleases_20220224_technote, accessed on March 17, 2025.