The processes of government procurement in the United States enable federal, state and local government bodies in the country to acquire goods, services (including construction), and interests in real property. In fiscal year 2019, the US Federal Government spent $597bn on contracts. The market for state, local, and education (SLED) contracts is thought to be worth $1.5 trillion. Supplies are purchased from both domestic and overseas suppliers. Contracts for federal government procurement usually involve appropriated funds spent on supplies, services, and interests in real property by and for the use of the Federal Government through purchase or lease, whether the supplies, services, or interests are already in existence or must be created, developed, demonstrated, and evaluated. Federal Government contracting has the same legal elements as contracting between private parties: a lawful purpose, competent contracting parties, an offer, an acceptance that complies with the terms of the offer, mutuality of obligation, and consideration. However, federal procurement is much more heavily regulated, subject to volumes of statutes dealing with federal contracts and the federal contracting process, mostly in Titles 10 (Armed Forces), 31 (Money and Finance), 40 (Protection of the Environment), and 41 (Public Contracts) within the United States Code. Value of government procurement In fiscal year 2019, the US Federal Government spent $597bn on contracts. This compares with $442bn in fiscal year 2015 and $461bn in 2016. Federal Procurement Reports provide contract data which may be used for geographical, market, and socio-economic analysis, as well as for measuring and assessing the impact of acquisition policy and management improvements. In Fiscal Year 2010, the top five departments by dollars obligated were: Department of Defense ($365.9 bn) Department of Energy ($25.7 bn) Health and Human Services ($19.0 bn) General Services Administration ($17.6 bn) NASA ($16.0 bn). The Top 100 Contractors Report for Fiscal Year 2009 lists contracts totalling $294.6 billion, the top five comprising aerospace and defense contractors: Lockheed Martin ($38.5 bn) Boeing ($22.0 bn) Northrop Grumman ($19.7 bn) General Dynamics ($16.4 bn) Raytheon ($16.1 bn) In the same period, small business contracts totalled $96.8 billion. Law The Federal Government's authority to enter into contracts derives from the U.S. Constitution, which defines its powers. The Federal Government acts through legislation, treaties, implementing regulations, and the exercise of those authorities. The Federal Government's power to contract is not set forth expressly and specifically in the U.S. Constitution, but Article 6 appears to assume the