Year	Number
1977	3.2346633925546278
1978	2.1733603584718986
1979	4.192470983262524
1980	4.511350573809472
1981	1.982279991363445
1982	1.923766725920921
1983	2.146419041547186
1984	2.1799985193814972
1985	3.1870827294055126
1986	4.307671253521175
1987	5.235721801116788
1988	5.239961111926691
1989	6.555890292847036
1990	6.320356420755039
1991	6.7664168734554035
1992	7.4691167228195
1993	8.906052524933182
1994	8.840241421598684
1995	8.12315443294953
1996	10.164420802722024
1997	10.853543977651832
1998	12.314901212344974
1999	8.20066047731833
2000	8.660906246533305
2001	8.578907466932801
2002	6.995541460162969
2003	5.6409527714577035
2004	6.200722939336776
2005	6.6128873153760885
2006	8.267873276776823
2007	7.3684637460757845
2008	5.899268363191949
2009	6.420066469977389
2010	4.951757641947001
2011	4.569376377725029
2012	5.012741903773307
2013	4.895416617802484
2014	4.476351527539009
2015	4.792398313635467
2016	5.864427227095021
2017	5.874030808763302
2018	5.031459509309323
2019	4.862085733074568
2020	6.146789774106966
2021	5.626110463325986
2022	4.539243562314488
2023	5.216112066841466