This chart by Mercatus Center senior research fellow Veronique de Rugy illustrates the gross amount of public debt that advanced economies must finance this year, represented as a portion of each nation's GDP.  This amount of debt, approximately $5 trillion for the United States, is an important metric – our public financing needs represent a massive amount of credit that will not be available for use by private investors; it also quantifies our susceptibility to credit market volatility. 

On average, each advanced economy shown here will require financing for debt equivalent to 23.7% of its GDP this year.