Year	% of total
1971	39.90291262135922
1972	39.90291262135922
1973	34.686609686609685
1974	48.35377663008393
1975	40.56545789797173
1976	39.28773318258904
1977	46.53567735263702
1978	43.35286164939161
1979	45.62864279766861
1980	48.61878453038674
1981	50.45078888054094
1982	57.905138339920946
1983	62.307020099038745
1984	58.85022692889561
1985	64.24469964664311
1986	63.16666666666667
1987	75.69357436907106
1988	77.58752484329612
1989	78.8756148981026
1990	84.26021727884118
1991	88.10157194679564
1992	86.59770631886666
1993	86.60656093851836
1994	84.63818479149631
1995	88.02517120118452
1996	87.10127244204287
1997	84.50834879406308
1998	84.58313926408943
1999	84.96885813148789
2000	88.78320968866907
2001	87.5517479300828
2002	89.2472542191267
2003	89.45819805194806
2004	91.1031884292833
2005	90.78156312625251
2006	90.97558497849717
2007	89.89517819706498
2008	89.81237944941259
2009	91.61578395244372
2010	92.69673939691101
2011	86.66002310148801
2012	84.1357439973642
2013	83.14947289156626
2014	82.01092309069746
2015	80.70359763433936