Year	% of total
1970	87.02363796085916
1971	86.77915807465402
1972	86.74584894206949
1973	86.99217644059152
1974	86.3572895176644
1975	86.60312810969747
1976	86.5325354137391
1977	86.48904877331803
1978	86.27458250078871
1979	86.21545485119391
1980	86.06690338650697
1981	85.54991102474946
1982	85.86718135028761
1983	85.55245501937735
1984	85.53068233618232
1985	85.21764218706068
1986	85.29612352005392
1987	83.82528066812705
1988	83.70774014758483
1989	84.23758679126519
1990	71.8836565096953
1991	72.06477732793523
1992	71.97875166002656
1993	71.94805194805195
1994	71.33507853403141
1995	73.12252964426878
1996	75.0330250990753
1997	77.6485788113695
1998	80.37267080745342
1999	80.95872170439414
2000	82.70270270270271
2001	82.22811671087533
2002	81.95876288659794
2003	82.76670574443142
2004	81.87203791469194
2005	82.75488069414317
2006	78.45238095238095
2007	79.05056759545923
2008	81.35874067937034