Year	% of total
1972	99.6667358756784
1973	99.76424099981637
1974	98.89258350961599
1975	97.81769370081138
1976	96.92652905627766
1977	95.96656855725038
1978	95.68672112263063
1979	96.46521918904082
1980	95.08826951967086
1981	95.71102699251597
1982	96.15465505872332
1983	96.82468187908773
1984	96.71696472035826
1985	96.44859037454458
1986	97.04685421613355
1987	97.34442937174802
1988	97.35880951234829
1989	97.40450230640059
1990	97.73626325534453
1991	97.9349347728737
1992	97.87203752194141
1993	97.92008101024194
1994	98.03966957407168
1995	98.17625649403357
1996	98.24575303130666
1997	98.35336113301814
1998	98.46664010310353
1999	98.44791916272446
2000	98.1679499065297
2001	98.11642758968637
2002	98.68775888863644
2003	98.66358482025412
2004	98.16494912742569
2005	98.45937932787496
2006	98.71576472964081
2007	98.4986961804817
2008	98.9208738980346
2009	99.25278799874798
2010	99.08168245842025
2013	98.12460861671839
2014	97.79178143263852