Year	% of total
1970	87.88717263494436
1971	87.60794254786752
1972	87.18310533810752
1973	87.43143377205874
1974	87.40347872884426
1975	87.39703169058451
1976	87.29926603183674
1977	87.20950395204902
1978	87.08856628282959
1979	86.86033896856708
1980	86.87192456996493
1981	86.7749229759101
1982	86.27205293249806
1983	86.2890419369528
1984	86.33368626410007
1985	86.1479807098594
1986	85.67124085835643
1987	85.75385190171927
1988	85.65665634891467
1989	85.29432259707866
1990	86.47023451593505
1991	85.52631578947368
1992	84.32203389830508
1993	84.06976744186046
1994	83.43767785998861
1995	83.34234721471066
1996	81.36387298282145
1997	79.44584382871537
1998	77.58284600389864
1999	75.95473833097596
2000	74.35897435897436
2001	73.7652922519257
2002	73.3630289532294
2003	73.03321678321679
2004	72.72727272727273
2005	72.37452551665965
2006	72.10940737670948
2007	71.56339762002462
2008	71.66732988460008