Year	% of total
1970	25.072602558511285
1971	24.583281235446393
1972	25.18378707094806
1973	24.53991704240109
1974	25.909368564420156
1975	25.224756985292984
1976	24.96396401593157
1977	23.79262772950855
1978	25.167484411216734
1979	24.922651177439896
1980	23.124681097938517
1981	24.584632942059496
1982	23.393036487702457
1983	25.344636964923282
1984	26.75021655379119
1985	27.907057090421322
1986	28.29607762580395
1987	27.55908301490958
1988	27.906140956959064
1989	26.95023386440586
1990	13.333333333333334
1991	13.48314606741573
1992	13.48314606741573
1993	13.138686131386862
1994	13.333333333333334
1995	13.846153846153847
1996	16.517857142857142
1997	16.8141592920354
1998	17.56756756756757
1999	19.523809523809526
2000	20.388349514563107
2001	17.21311475409836
2002	15.555555555555555
2003	13.782051282051283
2004	12.573099415204677
2005	12.011173184357542
2006	10.023310023310025
2007	11.671087533156498
2008	12.643678160919542