Year	% of total
1971	66.34146341463415
1972	67.01344836335956
1973	64.39547930726076
1974	51.070929691137664
1975	52.487097015483585
1976	51.815113315423304
1977	43.62056575423009
1978	40.86314152410576
1979	32.666389598052604
1980	37.862473080582966
1981	37.838112154275564
1982	35.858227848101265
1983	40.45341098169717
1984	41.3646162330175
1985	37.15197083618136
1986	32.91752707657297
1987	33.36216590260358
1988	34.42112751200427
1989	33.166666666666664
1990	31.858650037259284
1991	27.00218457606859
1992	33.57007575757576
1993	26.422392280818503
1994	21.069997643176997
1995	26.449220523687
1996	25.214111730965666
1997	27.401907955135112
1998	25.17099331571584
1999	25.23038605230386
2000	19.84219754529515
2001	19.64151180311401
2002	17.378616664597043
2003	20.664170915897504
2004	20.075508864084043
2005	19.07374330186272
2006	18.332213369172187
2007	18.725799512404993
2008	17.903337969401946
2009	16.49755005980169
2010	14.85581124381008
2011	14.274604072398189
2012	13.78847783112115
2013	12.365855369292278
2014	12.36186827758951
2015	12.511264644037249