Year	Number
1970	3.695097340205183
1971	4.428226488016721
1972	4.133239248300024
1973	4.371877180249776
1974	4.683392036747525
1975	3.3861865462303755
1976	3.436783551103345
1977	4.713649001106378
1978	5.486791370062873
1979	7.091678525214297
1980	6.515202390012903
1981	5.032147612534445
1982	5.055639881752851
1983	5.673559486342961
1984	4.837331210399977
1985	4.198781421318863
1986	4.459810117369237
1987	4.825050960339177
1988	4.320433661230966
1989	4.543025961049444
1990	4.271238890302457
1991	3.4394860256428808
1992	2.1133036913929235
1993	2.7425408738937045
1994	2.7763935495362806
1995	2.4716760645850306
1996	2.77599493986737
1997	2.899452906290875
1998	1.963283923349691
1999	1.660298253552759
2000	1.6849004371092995
2001	1.6517685545748668
2002	1.849338252983198
2003	1.7609537269098823
2004	1.503813636549883
2005	1.4636264462109818
2006	1.4617684972210392
2007	1.538632153414279
2008	1.58324580859698
2009	2.6290790177731638
2010	2.8782073669361488
2011	2.724804168549556
2012	3.360513070388971
2013	2.719295564098403
2014	2.634175913038268
2015	2.7876717359475913
2016	2.9269500050035453
2017	2.9368026697966787
2018	2.7026401317854782
2019	3.2680830259430738
2020	4.647484561448481
2021	3.829986524323349
2022	3.0925649380348785
2023	3.3434834155336315