Year	Number
1977	5.431100880126914
1978	4.350190345603672
1979	5.389468312929952
1980	3.611903613173692
1981	5.2263869598435395
1982	3.6370590665434808
1983	2.485175153679173
1984	1.1991741365829933
1985	2.255194665241151
1986	3.1502637260441384
1987	2.0679841017836753
1988	1.3243393052257366
1989	1.2040762028877527
1990	0.49107940862122235
1991	1.499310330970821
1992	2.21186730143576
1993	5.537440251976836
1994	5.379483289800968
1995	6.3807437571955115
1996	7.087934424045081
1997	4.831807381706086
1998	3.820486285375849
1999	3.4450155461823466
2000	2.6005007518495553
2001	2.677476539046605
2002	5.597773651439051
2003	4.332567505171589
2004	4.742771428848217
2005	2.531224575633179
2006	1.9588547113062755
2007	2.2298465221364636
2008	1.0843108489783624
2009	2.3519874119664537
2010	2.693239463258969
2011	2.8714432508008807
2012	1.940222844376742
2013	1.9709700911463632
2014	2.300295016383704
2015	2.2815276871976797
2016	1.7810103920372757
2017	1.8448471627707297
2018	2.3537373291229255
2019	1.8052786437251804
2020	2.048579015611746