This chart depicts the composition of the US Federal debt by instrument classification and how it has changed over time. This data is obtained directly from the Monthly Statement of the Public Debt (MSPD). An explanation of each kind of debt instrument can be found on treasurydirect.gov.

To some extent, the time frame in which the debt principal will need to be repaid or rolled over by the Treasury can be approximated by the instrument classifications. The duration ranges are as follows:

All of these instruments mentioned above are considered marketable, meaning they are freely traded on a public exchange. Nonmarketable debt pertains to certain issues of debt that are not publicly traded. They may have unique terms and are sold directly to specific investors rather than through a public auction. Nonmarketable public debt includes: