Year	% of total
1970	15.241589522148214
1971	13.280010279646353
1972	13.513805158730138
1973	13.68689598706053
1974	12.92894282185639
1975	12.418849276032047
1976	11.601022386495464
1977	13.76735964205935
1978	14.738612054020644
1979	12.825633319337992
1980	13.454175358361608
1981	13.70197876172269
1982	12.868241788022225
1983	15.948428076467469
1984	15.611563254218844
1985	14.98150099985002
1986	14.268356348098163
1987	13.43549816882177
1988	12.764326052298278
1989	13.211307861298838
1990	0.16339869281045752
1991	0.16025641025641024
1992	0.1567398119122257
1993	0.15432098765432098
1994	0.15128593040847202
1995	0.18115942028985507
1996	0.44943820224719105
1997	0.5882352941176471
1998	0.8547008547008548
1999	2.34375
2000	14.285714285714285
2001	12.5
2002	11.538461538461538
2003	10.344827586206897
2004	10.714285714285714
2005	13.333333333333334
2006	20
2007	27.500000000000004
2008	31.11111111111111