Year	% of total
1960	89.33975945488103
1961	89.61421351964283
1962	90.24593900972727
1963	90.48215583075728
1964	90.86472001675193
1965	91.11421493492654
1966	91.26485868739802
1967	91.43384413892046
1968	91.72587447833783
1969	92.1627322655627
1970	92.61986407562019
1971	94.15758517406512
1972	93.83968875450685
1973	94.19714101029844
1974	94.11100645370281
1975	93.87932226820604
1976	93.7962945186452
1977	93.78125504723937
1978	94.10004076740196
1979	94.07630005704603
1980	93.97684649265985
1981	93.16997835678055
1982	93.23252945848593
1983	93.2273671986631
1984	92.97035028709182
1985	92.95968732733252
1986	92.92992067612676
1987	93.07037635357351
1988	92.21663988436467
1989	92.66373953079204
1990	93.26899629494982
1991	93.1434904452662
1992	92.53043621004745
1993	91.87299822842219
1994	91.66273268979252
1995	91.33532679314395
1996	90.81706128957886
1997	90.47952165760718
1998	90.46900329497522
1999	90.1351115072162
2000	89.96115264316022
2001	89.9052741501404
2002	89.82742940609857
2003	90.13388127610632
2004	89.86812065662023
2005	89.78462827139023
2006	89.8525674246613
2007	89.88846972136196
2008	89.93664948376768
2009	89.08076391335088
2010	89.14323527269
2011	89.61960492433352
2012	89.38185917087756
2013	88.40710317362291
2014	89.32874706077632
2015	88.29755709217092