Year	Number
1977	5.817704024088946
1978	6.208167648187905
1979	6.776529488734932
1980	5.69451431054398
1981	3.4480595909789606
1982	3.5473537801180264
1983	3.7612315918134263
1984	3.632798674811181
1985	3.83949353324491
1986	4.272240047938843
1987	4.000865493568775
1988	2.964050177783039
1989	2.780209219286392
1990	2.852998376761618
1991	3.611219677188901
1992	4.721009090794771
1993	5.590466094853704
1994	6.161428234872395
1995	5.696986490189776
1996	5.96956518900299
1997	6.65343085828882
1998	6.753684261398472
1999	5.628372550271749
2000	5.516078759355534
2001	6.3509467080442645
2002	8.270860898304537
2003	9.535595906241412
2004	8.936068811525868
2005	7.487262293783931
2006	8.13356704082969
2007	9.10422561711446
2008	6.911333333511088
2009	8.824770519788133
2010	7.9285164104377595
2011	7.143477591734301
2012	7.177062865473212
2013	7.249400953264468
2014	7.251188716475389
2015	8.15578668956573
2016	8.539529086501572
2017	8.145067754229764
2018	6.921071875022922
2019	7.590697404707246
2020	11.374519552988529
2021	8.691973281515137
2022	6.447586806676964
2023	7.692113949967643