Year	Number
1987	0.8644859813
1988	0.7504708843
1989	0.6364557872
1990	0.5224406902
1991	0.4084255931
1992	0.294410496
1993	0.3127785766
1994	0.3311466571
1995	0.3495147376
1996	0.3678828181
1997	0.3862508986
1998	0.4046189792
1999	0.4229870597
2000	0.4413551402
2001	0.4522429907
2002	0.4631308411
2003	0.4740186916
2004	0.4849065421
2005	0.4957943925
2006	0.4957943925
2007	0.4957943925
2008	0.4957943925
2009	0.4957943925
2010	0.4957943925
2011	0.4957943925
2012	0.4957943925
2013	0.4957943925
2014	0.4957943925
2015	0.4957943925
2016	0.4957943925
2017	0.4957943925
2018	0.4957943925
2019	0.4957943925
2020	0.4957943925