Year	% of total
1960	38.243626062322946
1961	36.315789473684205
1962	27.881040892193305
1963	35.92677345537758
1964	31.00358422939068
1965	31.46067415730337
1966	31.33208255159475
1967	32.02725724020443
1968	29.985228951255532
1969	28.688524590163933
1970	28.82882882882883
1971	29.468599033816428
1972	29.385474860335197
1973	30.769230769230766
1974	30.98729227761486
1975	29.39585211902615
1976	29.392173189009156
1977	28.023598820058996
1978	28.85225110970196
1979	27.706635622817227
1980	27.292110874200425
1981	30.132450331125828
1982	30.748373101952275
1983	31.34171907756813
1984	13.871517907902216
1985	26.198212835093422
1986	24.86732373009856
1987	24.69691721510218
1988	23.181530676786842
1989	23.247744621790424
1990	18.942868157286043
1991	12.620840108401085
1992	13.601547433903576
1993	13.863426160337552
1994	10.624350775193799
1995	9.9165953307393
1996	13.250149597238206
1997	13.21325117370892
1998	14.196222222222223
1999	13.926933797909408
2000	14.627255555555555
2001	16.59756967670011
2002	14.897187500000001
2003	16.818571428571428
2004	18.06649581589958
2005	15.251537070524412
2006	15.707278582930757
2007	18.419493087557605
2008	19.706237471087125
2009	17.07144428152493
2010	17.27154437456324
2011	19.5122631913541
2012	20.303284714119023
2013	19.99093579978237
2014	18.719508830022075
2015	19.458416184971096
2016	16.791106219042376