Year	% of total
1971	97.72734651863497
1972	97.3084931261894
1973	98.10416347400923
1974	98.15357556889353
1975	98.26741605492671
1976	98.34472747775087
1977	98.44183104083352
1978	97.91164201525132
1979	98.3793787216851
1980	98.36808053442489
1981	98.35686781574597
1982	98.55704986596125
1983	98.32213945479666
1984	98.60389783170594
1985	98.68177381359243
1986	98.37627590636338
1987	98.34118226099379
1988	98.44487532340645
1989	98.72366736416501
1990	98.93136159386185
1991	98.91828560288609
1992	98.6788886589147
1993	98.73988173734311
1994	99.05873121145822
1995	99.13064470952025
1996	99.10415005762331
1997	99.27119702971821
1998	99.32626205613828
1999	99.57673240295742
2000	99.66519653782512
2001	99.58503846169005
2002	99.40728349042406
2003	99.22623307599513
2004	99.33232804571274
2005	98.89005328835559
2006	98.81113575323977
2007	98.8962223468227
2008	99.573039155522
2009	99.55557912843823
2010	99.44489988376837
2011	99.41712856867223
2012	99.32468489202707
2013	98.95888775813032
2014	99.02258054530185