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	97.55726641954186
2007	98.83555023703227
2008	99.97809323519103
2009	100
2010	100
2011	100
2012	100
2013	99.97298965889799
2014	99.97431475433896
2015	99.96840331414127