This report contains data on (1) the estimated percentage distribution of total U.S. R&D performance by national objective (table B-14) and (2) the reported distribution of Federal R&D authority by budget function (table B-21). (See Budget Function.) The performer based U.S. shares differ from the Federal budget authority shares for several reasons. The U.S. shares are based on expenditures reported by performers, who often expend Federal R&D funds in a year other than the one in which the Federal Government provided authorization, obligations, or outlays. In addition, the two series are based on slightly different concepts. For example, whereas in the U.S. series all of NASA's R&D funds are considered to be expenditures for space R&D, the budget authority data are distributed according to the functional categories that constitute the Federal budget. Thus, NASA's R&D budget authorizations are distributed between the space research and technology function and the transportation function.