Year	% of total
1960	2.230663541582478
1961	1.8942797244684038
1962	1.8929503916449086
1963	2.397706541568934
1964	2.756067461949815
1965	3.8229135507029617
1966	5.185625185625186
1967	7.031103908246589
1968	8.718594471427716
1969	10.210316061567385
1970	8.957569408067052
1971	10.104271423278464
1972	11.027780711946763
1973	12.385827561979323
1974	12.925574030087091
1975	14.645653971496667
1976	16.906507791017415
1977	17.060379021595416
1978	17.58908894340721
1979	19.277057197533487
1980	20.627348334529486
1981	21.176072139198173
1982	22.005065428450823
1983	20.87378640776699
1984	21.092993219244427
1985	21.131979046888972
1986	23.10697511083798
1987	22.69608268913402
1988	24.232769526308388
1989	25.378313253012045
1990	30.27912933847523
1991	31.358388845855927
1992	30.682674137931038
1993	32.80074340527578
1994	33.471370716510904
1995	36.586992860874105
1996	40.10742045843311
1997	39.018578698017194
1998	39.04220052310375
1999	39.17123467449491
2000	40.48265971078162
2001	43.57412078152753
2002	44.50761100125831
2003	46.752203331616
2004	47.56890406100373
2005	49.50056826304503
2006	47.315275874504145
2007	45.52090976606016
2008	45.611035263058646
2009	43.81390468227425
2010	46.9556746031746
2011	45.66747814964827
2012	44.17624683398572
2013	43.29147203140333
2014	39.35955451636722
2015	39.54408944213923
2016	41.33619154676259