Year	% of total
1960	38.72594732931554
1961	35.15968030182862
1962	31.542101416250564
1963	33.361600277987286
1964	27.566258857615544
1965	30.039278417337023
1966	31.793540772400604
1967	28.103839200526664
1968	26.845988906286735
1969	24.822415523166903
1970	22.26470887335421
1971	19.70674208459072
1972	19.04544962658568
1973	16.850220283270072
1974	18.141784105490217
1975	18.345243520640082
1976	14.120502863553414
1977	20.179458920903524
1978	18.040285616179716
1979	17.8975428902507
1980	16.2463984803935
1981	15.808381948671835
1982	15.880566710007102
1983	15.420602380729251
1984	14.770809405518314
1985	13.90532097043794
1986	13.241595399718816
1987	13.737579241675272
1988	14.343468865652179
1989	10.299597323818091
1990	11.024511639679014
1991	11.678922049047669
1992	11.96705738255992
1993	12.390590133505324
1994	13.528572279363601
1995	12.360586065879547
1996	12.798678282640818
1997	12.067443939169264
1998	11.942629741806678
1999	11.776731532346734
2000	11.706390120401874
2001	12.485754444170249
2002	10.056116320347098
2003	10.106191760928837
2004	10.085278942794613
2005	8.619090989726095
2006	9.167791311296677
2007	9.087827084206074
2008	9.559159165206651
2009	10.306540108532687
2010	11.274365718475122
2011	9.215732621283905
2012	9.836920459526372
2013	11.852245618125727
2014	11.989082690626526
2015	9.979026474842545