Year	% of total
1970	55.376056225285375
1971	55.09058618564815
1972	54.69630851019849
1973	53.91977538766235
1974	54.3461883639542
1975	55.54158955569457
1976	56.964586020030964
1977	56.11017805117765
1978	56.819979027041725
1979	57.56586935343281
1980	57.48177627496288
1981	55.98617343134122
1982	57.95319408417543
1983	57.50644493048262
1984	58.55086129967984
1985	57.86676801057503
1986	57.09226327969134
1987	57.39740409404664
1988	58.03767705198081
1989	57.515557172370045
1990	77.69516728624535
1991	76.86567164179104
1992	76.60377358490567
1993	77.01149425287356
1994	77.01149425287356
1995	76.53846153846153
1996	76.06177606177607
1997	76.09561752988047
1998	75.6
1999	75.10373443983403
2000	74.78991596638656
2001	75.93360995850622
2002	75.10917030567686
2003	75.22123893805309
2004	77.13004484304933
2005	77.97356828193833
2006	78.0701754385965
2007	78.125
2008	77.48917748917748