Year	Number
1960	9.46164199192463
1961	15.273833671399593
1962	18.372093023255815
1963	14.899057873485868
1964	20.854870775347912
1965	21.762652705061083
1966	25.109612141652615
1967	26.84992570579495
1968	18.603603603603602
1969	13.936170212765957
1970	16.273015873015872
1971	14.375596715146305
1972	9.110083871756329
1973	10.655670038057593
1974	13.50086317222241
1975	18.757227681280806
1976	8.748247641874858
1977	11.293111868733357
1978	6.346958664120312
1979	9.90247858001068
1980	12.530798875212259
1981	14.584722233649801
1982	19.506833229996047
1983	9.730720785561818
1984	10.00931146143203
1985	23.17315818886218
1986	14.07973683424397
1987	29.724656913430177
1988	23.41807290828675
1989	13.869495243535832
1990	6.5883820430186155
1991	5.994114268879501
1992	7.44726767770178
1993	7.4785034150290395
1994	7.343329844447783
1995	7.17247315320455
1996	6.940395799144072
1997	5.9594531407024505
1998	8.278679399258229
1999	10.415286565036185
2000	12.960350996583196
2001	9.254749646943075
2002	8.396332260662104
2003	10.169631796157574
2004	17.61423769840455
2005	9.962563998647116
2006	11.046289328973817
2007	8.840156466321167
2008	8.086855177849316