Year	% of total
1970	38.77581282805682
1971	30.163882269100924
1972	31.734393076031143
1973	32.98630761894133
1974	30.353484638015228
1975	33.63432186467076
1976	31.792950961626104
1977	33.879387349982544
1978	34.378658809038974
1979	37.44082623355317
1980	34.8732337785175
1981	32.47979740945674
1982	34.180398422139916
1983	33.60961587712883
1984	28.28911702524417
1985	28.795184512592087
1986	28.746134696065205
1987	34.810401084536466
1988	27.58876631954241
1989	30.701338253436244
1990	90.625
1991	90.50678087080657
1992	90.33404406538736
1993	90.3202846975089
1994	90.18492176386913
1995	90.07142857142857
1996	87.75510204081633
1997	87.56805807622504
1998	88.26086956521739
1999	87.22800378429517
2000	85.91817316841104
2001	87.59964570416298
2002	89.7841726618705
2003	90.40370615486432
2004	90.9090909090909
2005	90.65066329753633
2006	90.42883778744562
2007	88.9198606271777
2008	89.24802110817942