Year	% of total
1970	55.97463808485299
1971	55.21655094806812
1972	53.55665230049219
1973	53.55946596575916
1974	54.302993808430855
1975	53.70926949805707
1976	54.66718485777178
1977	54.99006534029072
1978	55.27374512054427
1979	55.78042711759592
1980	56.411076078098596
1981	57.25735152982849
1982	57.49759676159969
1983	57.03225243604394
1984	56.44378478537509
1985	55.14215571816044
1986	56.248776371668164
1987	58.346102833650704
1988	59.197570605197946
1989	60.15937079497709
1990	60.10928961748634
1991	61.94444444444444
1992	63.42857142857142
1993	66.29213483146067
1994	73.12348668280872
1995	75
1996	73.67088607594937
1997	72.26666666666667
1998	70.99447513812154
1999	71.54471544715447
2000	71.46666666666667
2001	71.00271002710026
2002	70.05494505494505
2003	70.1086956521739
2004	69.35933147632312
2005	68.99441340782123
2006	68.55524079320114
2007	67.64705882352942
2008	66.25386996904025