Year	% of total
1960	55.55001247193814
1961	53.14810340661995
1962	50.73904627837409
1963	47.744995578422696
1964	39.39279224712296
1965	35.09815368897321
1966	31.343970000353767
1967	27.867445054945055
1968	24.07156235871601
1969	20.86747445347844
1970	13.258926264661811
1971	9.28495197438634
1972	6.560386697961936
1973	6.242805277605598
1974	6.9045115875119984
1975	5.569268374511731
1976	5.441618222289456
1977	5.962186655952142
1978	6.461115053000493
1979	6.24402054005506
1980	7.158055653108021
1981	8.929841721500978
1982	9.565929565929567
1983	14.661963238999547
1984	17.430543266678463
1985	17.087195756704503
1986	16.129195309340883
1987	16.7379704850262
1988	19.2991214057508
1989	18.773326138765235
1990	20.148107178968655
1991	17.840036900369004
1992	18.14119404932794
1993	17.46267707082833
1994	19.19922119171643
1995	20.06429597176585
1996	18.25698769549218
1997	17.579485223450263
1998	17.41012161514498
1999	15.86673966839891
2000	15.65987492298213
2001	14.720573476702508
2002	17.00612298507463
2003	17.375547929132935
2004	16.79075336895911
2005	16.68346371375841
2006	16.568810091014598
2007	16.153243029824456
2008	16.12779369974001
2009	15.461519247539554
2010	14.787119654124794
2011	17.25361931138667
2012	19.152113382427626
2013	18.87646130346232
2014	22.189398892521183
2015	25.690569223958004
2016	23.906050420168068