Year	% of total
1960	18.639563616019394
1961	20.04076676207824
1962	20.029329096908224
1963	24.09625356021325
1964	22.480773023072373
1965	24.78407698514689
1966	19.635312430509227
1967	19.582252138838218
1968	18.21512379675303
1969	18.356831188194793
1970	17.998825459184705
1971	21.832406447356018
1972	20.821114369501466
1973	17.71591808852525
1974	18.964699797422526
1975	19.956781146794604
1976	19.72065137710755
1977	15.938269060579243
1978	16.180618691283772
1979	16.95552883289388
1980	13.589684356427325
1981	13.771916092673763
1982	13.021367071150145
1983	11.497673360690694
1984	10.839073037738556
1985	11.417349155941835
1986	11.566991561248743
1987	10.338115766824053
1988	10.338843333767192
1989	9.827851130661807
1990	9.169923583970133
1991	10.106940256554402
1992	9.645815265889922
1993	10.131956186135412
1994	9.783512493345057
1995	9.19244234831168
1996	8.69158087716824
1997	9.04276584209114
1998	7.887949379291248
1999	7.957196246077386
2000	7.795524720771548
2001	7.385459166610929
2002	6.9826456385402285
2003	7.377621426563789
2004	7.059194699688449
2005	6.704270255356978
2006	6.84321114438806
2007	5.901333037011429
2008	4.899351223706459
2009	4.757048711179186
2010	5.344130836608603
2011	6.59926666062771
2012	5.585644423913216
2013	7.2794356244066005
2014	7.405826056133794
2015	5.296183545006263