Year	% of total
1970	84.19571615951301
1971	84.67082879029685
1972	83.36878921055036
1973	81.95759447566272
1974	81.86027721012883
1975	82.38794586857932
1976	82.8601574731338
1977	82.1367597688968
1978	83.8308951242547
1979	83.88793086413247
1980	83.96025822792961
1981	85.50479131761952
1982	84.72901072730501
1983	83.77105676824695
1984	82.77283970955355
1985	81.92215076300262
1986	82.16508018299689
1987	82.12992470974238
1988	82.95457166862712
1989	82.71200700534187
1990	98.24000000000001
1991	98.23151125401928
1992	98.07692307692307
1993	97.94628751974723
1994	97.96557120500783
1995	97.99382716049382
1996	97.81976744186046
1997	97.28958630527818
1998	97.05093833780161
1999	96.9097651421508
2000	96.48058252427184
2001	96.14890885750962
2002	96.125
2003	96.10231425091352
2004	96.33225458468176
2005	96.30411826821542
2006	96.24217118997912
2007	96.18556701030928
2008	96.41472868217055