Year	% of total
1971	65.19607843137256
1972	46.38297872340426
1973	44.100294985250734
1974	48.78048780487805
1975	52.04081632653062
1976	55.38160469667319
1977	75.34602076124568
1978	70.03514938488577
1979	50.16429353778752
1980	47.06467661691542
1981	50.29126213592233
1982	55.78842315369261
1983	61.38952164009112
1984	43.36188436830835
1985	43.21705426356589
1986	52.137468566638724
1987	48.90453834115806
1988	47.734375
1989	35.47145606157793
1990	38.64104323953329
1991	39.747843397478434
1992	49.054301403294694
1993	42.997118155619596
1994	51.546391752577314
1995	54.55525606469003
1996	56.4977420973407
1997	58.23960880195599
1998	72.15357458075906
1999	72.62234533702677
2000	78.60484900042535
2001	80.1984126984127
2002	75.41984732824427
2003	72.94372294372295
2004	72.27926078028747
2005	65.38839724680433
2006	69.94256541161455
2007	71.00997506234414
2008	64.47485867301398
2009	69.09933391253982
2010	62.995353921836575
2011	66.0041841004184
2012	57.181840734309105
2013	47.69563130100816
2014	46.13135402609087
2015	49.94540292640314