Year	% of total
1964	25.901639344262296
1965	32.34880450070323
1966	15.342631898120073
1967	21.107266435986162
1968	19.643882825962088
1969	20.206409560021726
1970	16.756513926325244
1971	16.65268456375839
1972	19.61658493089612
1973	18.885815883050178
1974	20.728744939271255
1975	25.385632437197003
1976	15.215924426450744
1977	18.178233438485805
1978	18.34319526627219
1979	15.948777648428402
1980	17.465753424657535
1981	20.365332296929655
1982	16.47940074906367
1983	17.490361023484056
1984	18.403547671840354
1985	18.113612004287244
1986	14.441340782122905
1987	11.958614051973052
1988	14.301981325438398
1989	13.61576801087449
1990	11.313793103448276
1991	14.968573770491803
1992	16.458814293448835
1993	19.301129976580793
1994	23.16
1995	26.010116279069766
1996	26.8485598923284
1997	31.499609544468544
1998	28.1736105188344
1999	29.878400758533502
2000	24.036248175182482
2001	19.073676258992805
2002	20.28740592473979
2003	22.29737721021611
2004	18.57896622313204
2005	18.91069457659372
2006	19.398168870803662
2007	19.199149590163934
2008	21.18175
2009	21.528838709677416
2010	17.979887869520898
2011	28.404090513489994
2012	30.523005780346818
2013	33.28781553398058
2014	30.694148148148148
2015	29.247282258064516
2016	28.79545950864422