Year	% of total
1971	100
1972	100
1973	100
1974	100
1975	100
1976	100
1977	100
1978	100
1979	100
1980	100
1981	100
1982	100
1983	100
1984	100
1985	100
1986	100
1987	100
1988	100
1989	100
1990	100
1991	100
1992	100
1993	100
1994	100
1995	100
1996	100
1997	100
1998	100
1999	100
2000	100
2001	100
2002	100
2003	100
2004	100
2005	100
2006	99.99741046689282
2007	99.99743273772849
2008	99.99736800547456
2009	99.99741815553031
2010	99.75773048167348
2011	99.79543827349903
2012	99.7657295850067
2013	99.7573931252873
2014	99.734395750332
2015	99.72127267946358