Year	% of total
1970	0.5387045212551848
1971	0.7710304985023534
1972	0.7673552725082807
1973	0.7726538243978243
1974	0.8427005117726282
1975	0.8182277618217252
1976	0.8980570502938088
1977	0.8770463612017011
1978	0.8613843431348167
1979	0.8086842848647042
1980	0.9499326694909086
1981	1.0594615024626763
1982	1.0905250896187657
1983	1.2046959266095283
1984	1.4289322772373896
1985	1.5121160686718988
1986	1.5890681844356696
1987	1.46404886173749
1988	1.7887794643897403
1989	1.7765949319523449
1990	2.1844660194174756
1991	2.2974607013301087
1992	2.406738868832732
1993	2.5089605734767026
1994	2.622169249106079
1995	2.603550295857988
1996	2.588235294117647
1997	2.6602176541717046
1998	2.5791324736225087
1999	2.6602176541717046
2000	2.7777777777777777
2001	3.0104712041884816
2002	3.4532374100719423
2003	3.1407035175879394
2004	3.75
2005	3.1746031746031744
2006	3.414634146341464
2007	3.1425364758698096
2008	3.5108958837772395