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	100
2007	100
2008	100
2009	100
2010	99.9526963103122
2011	99.54107388710418
2012	98.8666085440279
2013	98.4451354953354
2014	96.65924276169265
2015	92.32540291634689