Year	% of total
1960	91.76526065381225
1961	92.10454800251851
1962	92.75396860184433
1963	91.04656541746809
1964	92.40352139560173
1965	92.82543251017957
1966	91.59480865932696
1967	93.64900655768504
1968	94.01785496114256
1969	92.4590134889005
1970	93.39177997872987
1971	92.50995477698093
1972	90.75550334306295
1973	92.18236470769821
1974	92.08240220872506
1975	92.72735644223296
1976	93.93108019586106
1977	91.59255098510663
1978	91.67016715310231
1979	91.40037469402806
1980	94.03165878065462
1981	93.34953373346153
1982	93.07060361320075
1983	92.00145714409199
1984	86.58322286717105
1985	85.40211513023198
1986	82.8923545525935
1987	81.85179412086868
1988	79.3042298683435
1989	77.60440170780001
1990	77.38649913588938
1991	77.9523570058137
1992	79.25417767178493
1993	77.69169530341983
1994	78.59018687112915
1995	79.60094520888593
1996	77.85351034423455
1997	80.06129404745712
1998	79.52609681435756
1999	80.97590440887573
2000	80.63494268797741
2001	79.8499960208187
2002	81.46071287465873
2003	80.82302301864463
2004	81.83202563415655
2005	83.4668123985147
2006	82.5095887666763
2007	83.18621647779008
2008	81.80831581898948
2009	79.71021291685348
2010	76.00086331064998
2011	76.50008868696364
2012	75.00814839911963
2013	72.55135062662742
2014	71.53112184817807
2015	72.95554611833776