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	77.22295225580376
1996	76.00529538308787
1997	77.81299524564183
1998	79.30218805440568
1999	77.0944679669605
2000	78.05885389778007
2001	77.95295139966483
2002	78.87171296560379
2003	79.64419574513013
2004	80.73376399230732
2005	72.05363443895554
2006	60.406398965823705
2007	55.999847526111154
2008	59.010674666852715
2009	60.80071115793633
2010	52.87179802199152
2011	40.19000730797339
2012	39.52443471918308
2013	41.61633212882125
2014	46.29879939572235
2015	46.299684458939886