Year	Number
1971	36.8015
1972	36.01959
1973	36.32402
1974	36.75235
1975	34.62123
1976	33.86258
1977	32.72545
1978	32.00104
1979	30.50427
1980	29.4374
1981	28.11262
1982	27.79374
1983	27.26846
1984	27.19603
1985	27.05551
1986	25.89366
1987	25.22223
1988	26.49236
1989	26.92287
1990	26.12085
1991	25.06963
1992	24.74328
1993	24.23779
1994	23.7348
1995	23.3829
1996	23.54409
1997	23.45652
1998	22.92187
1999	24.92838
2000	24.77985
2001	24.11964
2002	25.32848