Year	Number
1971	11.0082
1972	14.292
1973	14.811
1974	13.29073
1975	11.67002
1976	13.59732
1977	12.21894
1978	12.14804
1979	10.04408
1980	10.55603
1981	11.84188
1982	12.29476
1983	13.21697
1984	12.77297
1985	14.29205
1986	16.55804
1987	18.2106
1988	15.4392
1990	16.1437
1992	11.95426
1993	12.49322
1994	13.24854
1995	16.37796
1996	16.41224
1997	17.45062
1999	17.9302
2004	17.02818