Year	Number
1974	11.64581
1975	12.30591
1976	14.32644
1977	14.68301
1978	14.95898
1979	15.06217
1980	15.00086
1981	15.1223
1982	15.17498
1983	15.04644
1984	15.82406
1985	15.89167
1986	16.41143
1987	16.51431
1988	16.74193
1989	17.01005
1990	17.01357
1991	16.60783
1992	16.49001
1993	16.62152
1994	15.13889
1995	14.84516
1996	14.68062
1997	14.27613