Year	% of total
1970	59.8352772577029
1971	59.4833809285483
1972	59.34955728622899
1973	59.14412122389345
1974	58.91662899653587
1975	59.99411480434538
1976	58.601771995043364
1977	55.024543762901224
1978	53.73445972150065
1979	52.30832522294433
1980	52.706387451833606
1981	54.042533494861885
1982	54.44914807419012
1983	55.18119206023605
1984	55.86158942830549
1985	55.15629321413507
1986	53.72822917160606
1987	54.330407363834624
1988	52.243570258122794
1989	53.20549532142406
1990	29.09090909090909
1991	28.846153846153843
1992	29.411764705882355
1993	29.166666666666668
1994	30.434782608695656
1995	31.818181818181817
1996	28.888888888888886
1997	29.78723404255319
1998	28.000000000000004
1999	27.450980392156865
2000	28.30188679245283
2001	27.77777777777778
2002	26.785714285714285
2003	27.586206896551722
2004	27.11864406779661
2005	25
2006	26.5625
2007	28.35820895522388
2008	28.985507246376812