Year	% of total
1970	70.21984765757854
1971	70.00880499289639
1972	67.94183546461235
1973	66.94464312481844
1974	65.67400220096923
1975	66.3273120121564
1976	66.45873008072502
1977	67.0653520356486
1978	66.5889902831011
1979	66.20338174596094
1980	65.69003016438388
1981	64.1625909926025
1982	65.29643854071678
1983	62.79088444963583
1984	62.55545115356595
1985	62.91575508144762
1986	63.927302370778385
1987	65.03230680013255
1988	64.00597896643228
1989	64.67412510542437
1990	69.54612005856515
1991	69.472182596291
1992	69.08077994428969
1993	68.9280868385346
1994	68.6092715231788
1995	68.1462140992167
1996	68.67167919799499
1997	67.87954830614805
1998	66.79340937896072
1999	67.90419161676647
2000	68.89897843359817
2001	67.09451575262544
2002	64.92718446601941
2003	62.92134831460674
2004	64.69221835075494
2005	64.97747747747748
2006	65.06550218340611
2007	63.19910514541387
2008	63.77277599142551