Year	% of total
1960	98.2469031231268
1961	98.30405988617062
1962	98.39621714892378
1963	98.42085721457043
1964	98.51842370724432
1965	98.48322188231803
1966	98.38041687988124
1967	98.31815928977687
1968	98.3266400666609
1969	98.3094082750672
1970	98.51603953277217
1971	98.40003407221528
1972	98.26794321575471
1973	98.66049858790944
1974	98.69160455994891
1975	98.53120515681304
1976	98.66290759905787
1977	98.6172507561971
1978	98.86159799517642
1979	99.0083998374476
1980	98.89705035969236
1981	98.56129193618156
1982	98.87214426086646
1983	98.89132840826318
1984	98.77884300269045
1985	98.5598041581933
1986	97.84634048601613
1987	97.98890245619786
1988	97.79065687748037
1989	97.89936156850955
1990	97.80680713313512
1991	98.05065912629333
1992	98.04603324369624
1993	95.58676875122154
1994	95.33847707321208
1995	95.45551646072143
1996	95.89704630302501
1997	95.89721099215625
1998	96.10865233975404
1999	96.31842863673408
2000	96.21984176705291
2001	95.98089994469619
2002	95.87003043771405
2003	96.24775866466713
2004	95.9787564750952
2005	95.99393988720713
2006	95.82033864257387
2007	95.21206560207278
2008	94.11388883610816
2009	93.15405778543386
2010	92.45120756925895
2011	92.11514123463645
2012	90.97851870869306
2013	91.14640642360806
2014	90.08796429578791
2015	90.29137543565525