Year	% of total
1971	43.21634675791054
1972	45.05555371523996
1973	48.18456094479564
1974	45.66960243125095
1975	42.34108013033073
1976	44.4081721285299
1977	45.80971349930641
1978	49.042938675980395
1979	48.278171808498804
1980	50.81527044966408
1981	48.57610773268397
1982	47.02899240942857
1983	56.16419512419425
1984	56.651432367760904
1985	55.12424673272079
1986	53.39234964770697
1987	56.160062647090406
1988	59.87147929033133
1989	59.779450065229
1990	63.83794083649942
1991	65.09220970724544
1992	66.86594732886809
1993	71.73378721497573
1994	75.13667779520301
1995	75.98236301197315
1996	77.83562549858198
1997	78.83596273754604
1998	78.56600058322657
1999	78.7011377194672
2000	78.74346473650861
2001	81.19440353403557
2002	81.92836083606862
2003	82.03147041459565
2004	82.05719878988013
2005	81.81330375758536
2006	81.56143348166609
2007	81.15233514756082
2008	80.5707908532285
2009	80.1335424858594
2010	79.9930566926308
2011	80.19388910617715
2012	80.16213660826187
2013	80.66699694913987
2014	79.83902265055004