Year	% of total
1970	51.27014351259955
1971	52.06341786213532
1972	51.84991673307587
1973	50.74226320031272
1974	50.22116607806518
1975	51.442364411280096
1976	51.009655778871696
1977	50.68888854379271
1978	50.98860575236759
1979	50.90847259482213
1980	51.86308701731741
1981	52.25234713051874
1982	54.413643988572126
1983	55.830262984290734
1984	54.21201264964988
1985	55.08672985010882
1986	55.84561923876888
1987	56.508175712470496
1988	57.0359392077634
1989	57.42846441452749
1990	76.27986348122867
1991	74.95527728085868
1992	77.80082987551867
1993	74.40758293838863
1994	76.17801047120419
1995	74.05405405405405
1996	71.98067632850241
1997	70.51886792452831
1998	65.92427616926503
1999	64.95535714285714
2000	62.046908315565034
2001	59.28270042194092
2002	58.517034068136276
2003	57.760314341846765
2004	55.82706766917293
2005	53.3213644524237
2006	53.2608695652174
2007	48.48966613672496
2008	49.58263772954925