Year	Number
1970	15.53808
1971	13.83628
1972	19.20092
1973	15.10582
1974	15.10381
1975	17.15009
1976	18.24416
1977	17.19175
1979	20.92302
1982	23.98685
1983	20.75102
1984	16.8124
1986	14.06989
1987	13.92642
1991	14.78826
1992	15.7124
1995	16.58034
1997	14.72865
2002	15.32962