Year	% of total
1960	26.59690429474602
1961	32.946145723336855
1962	39.599932191896926
1963	36.84891620834681
1964	39.8635477582846
1965	42.12076583210604
1966	43.5313262815297
1967	48.80770072194268
1968	51.24709683934162
1969	50.87404327695361
1970	51.51358789129687
1971	55.00499347007759
1972	57.07768775107238
1973	60.12205646652693
1974	60.06477927063341
1975	59.89060058048673
1976	59.57520891364902
1977	62.175769835918196
1978	63.589329789253846
1979	57.763221737020864
1980	59.5082522627172
1981	56.43650720778625
1982	55.0333024196948
1983	54.19788586934511
1984	51.167508804164754
1985	47.77678510068037
1986	46.021835979167975
1987	47.75306272229436
1988	46.65118304543475
1989	45.3648136449779
1990	44.05562562850165
1991	41.190644555694625
1992	42.12289728358807
1993	45.97003791042858
1994	45.00788085493406
1995	45.93666111969571
1996	43.727170665947696
1997	40.979326411488195
1998	38.94189424812999
1999	39.970623217711406
2000	37.79742221401533
2001	38.431376276671045
2002	38.275149433019415
2003	35.64265103121007
2004	34.43975868210152
2005	32.44922854346623
2006	29.07729173848098
2007	26.460976571962487
2008	25.95372876044568
2009	23.6508313935309
2010	23.7036894184168
2011	23.456011897268038
2012	23.39708343468742
2013	24.34716503755854
2014	23.319209135744483
2015	26.034771751187463
2016	26.531149790437546