Year	Number
1976	8.57777689646219
1977	8.05911856114923
1978	9.060555512498693
1979	7.936527313818657
1980	6.33100054769486
1981	6.672351113943716
1982	7.46554689618083
1983	8.110699006392174
1984	6.984366286281021
1985	7.034152158992893
1986	7.276957280611674
1987	7.060259142339763
1988	5.93278395463576
1989	5.175373102358166
1990	4.569967135952482
1991	4.284182764339302
1992	3.5785903671244754
1993	3.891712937331737
1994	4.302358395073249
1995	3.2564203369688483
1996	3.4043419788888856
1997	3.0857541620689757
1998	3.1929492325064928
1999	3.2606973970227453
2000	2.9481775027348642
2001	3.5029200546627584
2002	4.276513817640959
2003	4.363837084842291
2004	3.67343193081051
2005	3.06430218727203
2006	3.4815259299038446
2007	3.2823265043014636
2008	2.723505546534537
2009	4.204489857057539
2010	4.460735769179341
2011	5.119461892375977
2012	3.882543632415078
2013	3.8017215438666017
2014	3.996610361984783
2015	4.597110377051898
2016	5.591980144899945
2017	4.974765141701329
2018	4.568023883386089
2019	5.097494367097802
2020	6.637758650998011
2021	5.63044057568032
2022	4.150477458204368
2023	4.124995182775501