Year	% of total
1960	14.327558492587963
1961	26.978363591146483
1962	35.98723648135814
1963	31.48283727085856
1964	42.29171308370795
1965	40.891590188149266
1966	43.021746912475386
1967	49.10933277904802
1968	52.65039579114629
1969	57.43440499215414
1970	58.98829144348304
1971	62.352324080051645
1972	63.567448877470234
1973	69.07223658245087
1974	69.15455298125602
1975	66.51963945176914
1976	71.07545292150597
1977	64.68555632342779
1978	68.96354530698537
1979	70.7260934418628
1980	71.97859097201783
1981	72.50131318662896
1982	71.51837470988748
1983	71.89424182023109
1984	70.6294952014073
1985	71.83447927698546
1986	71.65779930649303
1987	78.02029330482318
1988	77.74129254073446
1989	81.94577891509547
1990	83.59958150947469
1991	79.10404716890442
1992	79.26644151831425
1993	79.217729641175
1994	78.71819533094343
1995	82.30649972194604
1996	80.45263536036225
1997	80.87407311255699
1998	81.21858429756954
1999	79.68486625137413
2000	80.6702205296713
2001	79.43205808145821
2002	82.0251358401914
2003	82.92778348318767
2004	80.58266869972987
2005	82.79982482145265
2006	82.67060135005573
2007	83.63062987067764
2008	80.61379083779069
2009	75.15736903254894
2010	73.26164010804189
2011	71.36984114313084
2012	67.96480299228384
2013	60.036330924007245
2014	55.48907650045305
2015	60.24676625396893