Year	% of total
1971	10.546871320678756
1972	11.50183119783592
1973	12.603020225477357
1974	11.989585474435485
1975	12.203572368006151
1976	13.01953786062025
1977	12.927771911223932
1978	13.089687401773134
1979	13.251002464965932
1980	13.551121343327344
1981	12.764356488453604
1982	12.151342357609165
1983	12.420576377051741
1984	11.62942804642872
1985	10.428878843318735
1986	10.094993118970004
1987	9.535733973678065
1988	8.984238686656782
1989	8.506105146769958
1990	13.860821326528391
1991	13.528042338136867
1992	12.667334543117567
1993	11.906683656236767
1994	11.223507070916908
1995	11.011301795133946
1996	10.437426606540846
1997	10.292364794821921
1998	10.516943842968404
1999	9.653939658155565
2000	9.247638581699084
2001	8.435062382591978
2002	7.862614395603533
2003	6.8557466501338995
2004	6.731933767009808
2005	5.869138556203427
2006	5.3527789331692635
2007	4.7994369532536165
2008	4.660655832399394
2009	4.371411959119619
2010	4.026226119074376
2011	4.2842030005244425
2012	4.223267061314368
2013	4.058085942858053
2014	3.7408464983063494
2015	3.34670681568853