Year	% of total
1970	79.17105443426799
1971	79.95325068679962
1972	78.96937444671151
1973	77.90765108811503
1974	77.18210226192738
1975	78.62114027319468
1976	78.19861824105418
1977	77.85264388055634
1978	77.63520070033968
1979	77.3091440167073
1980	77.37848348855219
1981	76.99265753532491
1982	76.98681383101409
1983	77.54635215762453
1984	77.74273144782013
1985	78.0102354034521
1986	77.96914616934588
1987	78.25975666575827
1988	78.10906614682085
1989	77.41290628947635
1990	90.98039215686275
1991	90.08264462809917
1992	91.59663865546219
1993	91.13300492610837
1994	90.41916167664671
1995	89.36170212765957
1996	89.5104895104895
1997	89.58333333333334
1998	89.86486486486487
1999	90.41095890410958
2000	90.14084507042254
2001	90.66666666666666
2002	90.60402684563759
2003	89.5104895104895
2004	89.54248366013073
2005	89.74358974358975
2006	89.24050632911393
2007	89.63414634146342
2008	89.88095238095238