Year	% of total
1960	4.845252403846154
1961	7.8813498602851615
1962	9.519907122857338
1963	11.648850490554986
1964	11.614134368625386
1965	12.321684420357565
1966	12.440469276338714
1967	12.532169631867518
1968	13.24380274961516
1969	11.783952959028833
1970	12.436840705611205
1971	12.402078007751298
1972	13.841210444968683
1973	15.09433962264151
1974	15.628117565804619
1975	16.57524721878863
1976	16.51477289431133
1977	16.786727788692428
1978	16.01643444087174
1979	16.28738944648713
1980	18.008295956564258
1981	20.09199698134905
1982	22.496808963267622
1983	24.982573539662624
1984	25.64976419153843
1985	28.662559690883242
1986	29.73714768288821
1987	31.95405965863774
1988	34.794421300489034
1989	38.12909085214995
1990	43.31790665064103
1991	44.93223984048614
1992	45.032194690265484
1993	36.7822921732865
1994	37.5302838063439
1995	46.77752921535893
1996	45.50429440581543
1997	48.346105874960735
1998	46.30492753623188
1999	50.43183918324764
2000	52.68237207186718
2001	51.94353807960279
2002	53.34896569336852
2003	53.853705983172325
2004	58.49879661614382
2005	56.06510183160196
2006	54.024348329793405
2007	53.320864755851616
2008	53.63873446327684
2009	55.93665650406504
2010	51.74234269061496
2011	52.27429933431118
2012	53.46963759592225
2013	49.3669875
2014	53.74434772942027
2015	52.85611317104627
2016	55.496506945951815