Year	% of total
1960	27.32897085068412
1961	30.003452641270577
1962	32.54380272550292
1963	33.376288659793815
1964	37.44821092278719
1965	38.66909928941809
1966	41.97646179712311
1967	46.07762180016515
1968	49.42419257078535
1969	50.1230718739744
1970	48.92216435185185
1971	53.293960486535894
1972	53.90890107021665
1973	55.76278417748522
1974	51.09111791730475
1975	53.11804759657521
1976	54.65787821720025
1977	55.912856304220206
1978	55.4797142128094
1979	56.14097755551586
1980	49.88782950084128
1981	53.4722675899915
1982	53.23349217154526
1983	50.860609480812634
1984	46.77332616294703
1985	46.33639471743648
1986	51.42392188771359
1987	53.7499206198006
1988	51.42307163481369
1989	51.43650901206125
1990	47.44381843143985
1991	48.219698814482534
1992	50.39184151205133
1993	52.21985640138409
1994	50.85611254074455
1995	49.101118012422354
1996	49.97064406779661
1997	49.272100591715976
1998	52.55825421370033
1999	50.76221411578112
2000	49.4262883677003
2001	49.57010749521425
2002	49.85893613954159
2003	49.82904378189632
2004	48.986862796833776
2005	49.48814664218258
2006	49.393153846153844
2007	50.243665075800116
2008	48.827662943588294
2009	50.63328935113319
2010	48.30627787307032
2011	46.93459206093452
2012	47.62425433881124
2013	48.131117870722434
2014	49.1693886110663
2015	48.93978780680918
2016	49.39661303044644