Year	% of total
1971	96.43529508305407
1972	95.8791694540124
1973	96.41956378774226
1974	96.34333809976008
1975	96.43245665376429
1976	96.87776621982445
1977	96.7190005672088
1978	96.94843663028759
1979	97.16215411418064
1980	96.81329351210563
1981	96.9062099559286
1982	96.68707968115865
1983	96.95942480575278
1984	96.73971091939514
1985	96.0478597558459
1986	96.41432315262306
1987	96.6040766083385
1988	96.01775710869624
1989	96.38813486397554
1990	96.14829080945793
1991	94.98322938005424
1992	94.81981937702983
1993	94.69313867855223
1994	94.48810756594736
1995	93.15785780947732
1996	90.95449501834109
1997	85.93158748490633
1998	85.23059120338593
1999	84.32978360032783
2000	84.81660271599632
2001	86.53529640081965
2002	86.74474721266574
2003	86.86267928581952
2004	84.48008926101312
2005	83.8666846203507
2006	85.0588612884279
2007	83.17948136042601
2008	79.84316277383851
2009	76.59493576420748
2010	75.07095149137302
2011	77.65183820399652
2012	76.42720092462879
2013	73.4937634512981
2014	72.52369457441283