Year	Number
1977	3.2346633925546278
1978	2.1733603584718995
1979	4.192470983262526
1980	4.511350573809475
1981	1.9822799913634443
1982	1.923766725920921
1983	2.146419041547186
1984	2.179998519381496
1985	3.1870827294055126
1986	4.307671253521174
1987	5.235721801116787
1988	5.23996111192669
1989	6.555890292847038
1990	6.320356420755039
1991	6.766416873455402
1992	7.4691167228195
1993	8.90605252493318
1994	8.840241421598684
1995	8.123154432949532
1996	10.164420802722026
1997	10.853543977651832
1998	12.314901212344974
1999	8.200660477318332
2000	8.660906246533305
2001	8.578907466932797
2002	6.995541460162971
2003	5.640952771457705
2004	6.200722939336777
2005	6.612887315376087
2006	8.267873276776823
2007	7.368463746075784
2008	5.899268363191948
2009	6.420066469977389
2010	4.951757641947002
2011	4.569376377725028
2012	5.012741903773307
2013	4.895416617802486
2014	4.47635152753901
2015	4.792398313635469
2016	5.864427227095019
2017	5.874030808763301
2018	5.031459509309323
2019	4.862085733074568
2020	6.146789774106969
2021	5.626110463325985
2022	4.5392435623144864
2023	5.2161120668414656