Year	% of total
1971	33.56181868109303
1972	33.96109881054544
1973	36.4046208063665
1974	37.596521428587245
1975	38.56571736106057
1976	39.41786370475238
1977	40.46693275851993
1978	40.155340898022125
1979	42.325530738096155
1980	43.25871274683287
1981	42.43517198216625
1982	41.4629777277512
1983	41.165433202848526
1984	43.67615209372497
1985	41.107195489203555
1986	43.27245205193412
1987	46.346516700029184
1988	43.121002752191025
1989	42.29948019576253
1990	43.25662537150231
1991	42.38659571442399
1992	45.4054069246184
1993	44.839300449472546
1994	44.03001348142074
1995	45.648703504599595
1996	45.423448556076714
1997	47.06853974362963
1998	48.44878567984672
1999	49.71395543497981
2000	50.30181178821712
2001	53.25673853875437
2002	52.27381622298578
2003	51.18695545729659
2004	54.5728908406231
2005	55.16465542933779
2006	54.76652330550791
2007	53.61726289988478
2008	53.48385073490729
2009	44.523718193924026
2010	46.08066251014357
2011	47.49721650020717
2012	45.77369170196944
2013	52.1727077058779
2014	53.909117209717174