Year	Number
1960	7.449696722293148
1961	6.781772482826376
1962	5.925647112466682
1963	6.420857039368277
1964	6.380506620115824
1965	6.697722524079543
1966	9.69119473566798
1967	11.035138982077902
1968	10.672100242678322
1969	11.972605565702297
1970	8.899282093862185
1971	8.224026881461615
1972	8.432468133041613
1973	9.1910032700334
1974	9.105868792652933
1975	12.137285605587765
1976	14.109461382987636
1977	16.192577197028292
1978	15.043790272887149
1979	10.390574888634626
1980	10.733614696329465
1981	17.977536651994516
1982	17.609719967064642
1983	19.843248850144683
1984	26.0328505408749
1985	25.36131077957612
1986	22.412680972227076
1987	17.19783164536968
1988	15.064294689229314
1989	17.68444229725772
1990	18.558516932218314
1991	22.17213634539719
1992	31.599717648951007
1993	29.965052313295622
1994	31.922527325737434
1995	28.02013110884278
1996	22.276893557501257
1997	26.375093241853367
1998	19.645232610898304
1999	17.33011400190157
2000	16.3323084290788
2001	33.363061789061874
2002	31.13244938618001
2003	35.93873251500938
2004	42.939009841444246
2005	52.77866244059087
2006	59.716940904484396
2007	40.0753418245139
2008	43.41321945593218