The National Defense Budget Estimates, commonly referred to as “The Green Book,” is a convenient reference source for data associated with the current budget estimates of the Department of Defense (DoD). It also provides current (nominal) and constant dollar historical data for the DoD, as well as selected data on all National Defense, the total Federal Budget, and the U.S. economy. 
The Green Book funding data are provided in three standard categories:
- Budget Authority (BA) (both discretionary and mandatory authority is included in most tables),
- Total Obligational Authority (TOA), and
While DoD analysts distinguish between BA and TOA, BA is what the general public recognizes as the amount of funding appropriated to the DoD by Congress (in most cases). It is authority provided to the Federal government to incur legally binding obligations (signing contracts and placing orders), which will result in current year and future outlays. On the other hand, TOA is a DoD financial term expressing the value of the direct Defense program for a fiscal year, exclusive of the obligation authority from other sources such as reimbursable orders accepted.
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