Gross Federal Debt Held by the Public as Percent of Gross Domestic Product (FYPUGDA188S) (https://fred.stlouisfed.org/series/FYPUGDA188S) was first constructed by the Federal Reserve Bank of St. Louis in January 2013. It is calculated using Gross Federal Debt (FYGFDPUB) (https://fred.stlouisfed.org/series/FYGFDPUB) and Gross Domestic Product (GDPA) (https://fred.stlouisfed.org/series/GDPA): FYPUGDA188S = (FYGFDPUB/GDPA)*100