Year	Number
1960	4.807712715336033
1961	7.162455691742283
1962	13.683563965959255
1963	11.837170122095015
1964	11.676953903097024
1965	12.467550482531756
1966	13.854254453297626
1967	14.33411077051097
1968	6.89049065655495
1969	6.385423138564897
1970	7.3834902008734895
1971	7.622892875663997
1972	5.3813332163135845
1973	3.919331154448736
1974	5.683378274910344
1975	5.2158654680540035
1976	3.2033580836359756
1977	2.5954495282137
1978	2.237378632325778
1979	1.4342341348616336
1980	1.4856900349174718
1981	1.8987779550059216
1982	2.1977259893129713
1983	3.680505307497129
1984	6.988801202312012
1985	4.965683179581559
1987	2.851005359719485
1988	2.4483428269495526
1990	2.3699987202898987
1991	1.795028472701302
1992	1.989393580424448
1993	2.3509337451342347
1994	3.2377195538942103
1995	3.603724689789807
1996	3.2665996824507637
1997	3.6878240896589225
1998	3.7178447572817377
1999	3.6494013818480733
2000	2.8634372396944614
2001	2.732911170376485
2002	2.4797532033443073
2003	2.369069324926793
2004	2.4958828198299163
2005	3.00945891100324
2006	3.384053231667929
2007	3.322596294944137
2008	3.684238719748597
2009	3.434832703532129
2010	3.871204964826025
2011	4.1642913699767306
2012	4.282868031500053
2013	4.017373175500876
2014	3.777282553347824
2015	3.1107124435063804
2016	2.9953488025549353
2017	3.2439294669924847
2018	3.350950659349812
2019	2.9879822414344033
2020	2.693268331293072
2021	2.9989945666304005
2022	2.980551595736394
2023	2.987689057731414