"With the WMEAT [World Military Expenditures and Arms Transfers] 1997 edition, the data series on US arms exports in dollar value terms is revised upward substantially using a new interim methodology, in the interest of improved accuracy. The revision was made in one of the two major component types of exports, namely, the 'commercial' arms sales made directly by US firms to foreign importers under authorization of the Department of State in accordance with the US Government's International Traffic in Arms Regulations. The other major type is exports under the 'Foreign Military Sales' (or FMS) program administered by the Department of Defense, which serves as an intermediary in transfers to other governments. After the present data revision, commercial exports made up 52% of total US arms exports over the past decade, FMS sales, 47%, and several minor types of exports, one percent. [...] [This] table…shows US commercial arms exports in three forms: reported ('preliminary' or partial) deliveries, total approved licenses and authorizations (both as reported by the Department of State), and the present estimate of deliveries based on 50 percent of authorizations, distributed over license duration. Also shown is the ratio (in percent) of partial deliveries to authorizations."
Federation of American Scientists: http://www.fas.org/