Year	% of total
1970	51.70548663539808
1971	51.0702629322216
1972	50.29097531753034
1973	49.89144280918418
1974	49.768170601560946
1975	50.12578537575837
1976	50.00169439731367
1977	50.21736491569315
1978	49.251727517872304
1979	49.38995582367791
1980	50.805434827229114
1981	49.75847617541562
1982	52.42980591309121
1983	54.6138773600911
1984	51.471770540475816
1985	49.45537145859093
1986	51.485974419000144
1987	51.624502500496064
1988	49.90650635999512
1989	49.28616039350383
1990	60.747663551401864
1991	62.16216216216216
1992	64.1025641025641
1993	64.65517241379311
1994	63.716814159292035
1995	64.34782608695652
1996	63.06306306306306
1997	61.46788990825688
1998	60.909090909090914
1999	60.36036036036037
2000	59.82142857142857
2001	59.29203539823009
2002	58.4070796460177
2003	60.68376068376068
2004	57.65765765765766
2005	55.96330275229357
2006	44.827586206896555
2007	43.373493975903614
2008	42.168674698795186