Year	% of total
1960	95.93482569772576
1961	94.71736964463634
1962	93.6196257713158
1963	93.07570871960232
1964	91.98405371380612
1965	91.04461513570982
1966	89.93168076539988
1967	88.61558775731311
1968	88.0855190103067
1969	86.89443124499726
1970	86.36549410232769
1971	84.07512758303353
1972	82.80054951327138
1973	80.98620344989475
1974	78.61591335911578
1975	79.20521110079703
1976	76.1692800539538
1977	76.27398027006228
1978	76.48650614314698
1979	76.82925632647454
1980	76.58051471231447
1981	77.56955041078447
1982	79.09319373185656
1983	79.35825324513917
1984	80.19073404319803
1985	80.6389897889924
1986	80.17255894493746
1987	80.17882716858644
1988	79.94286324475485
1989	79.7914176746877
1990	91.02507159421357
1991	89.11508137903475
1992	87.52240887775105
1993	84.37846720105314
1994	86.20203003003002
1995	83.37005397310098
1996	86.87385359296286
1997	83.47665622552857
1998	75.70179161046
1999	75.58873313857488
2000	71.72026916141611
2001	68.92587506911462
2002	73.02532779459763
2003	75.27241834908118
2004	74.94252216492934
2005	76.0941948267092
2006	76.32865822127486
2007	71.24770038393238
2008	79.69641330588838
2009	72.76236661564126
2010	77.61191904440905
2011	78.84861200118557
2012	78.3672912481735
2013	75.47377043439056
2014	75.10046714785537
2015	73.98380452330163
2016	70.83180489509706