Year	% of total
1970	51.43591798922558
1971	46.715126813830025
1972	46.54012325127981
1973	45.38202202432669
1974	48.747858261813846
1975	48.71382058112451
1976	45.29476376420571
1977	49.037837013619324
1978	49.44276713875107
1979	50.68331422551976
1980	52.050323345513775
1981	55.83307439701021
1982	56.71256517083349
1983	56.69721472928312
1984	54.89123188104649
1985	51.896025979968016
1986	51.95740955020158
1987	52.422463297788624
1988	51.70690822823727
1989	50.226927353849234
1990	52.12765957446809
1991	52.23033252230332
1992	52.63157894736842
1993	53.11526479750779
1994	54.0168324407039
1995	53.78277153558052
1996	53.377386196769464
1997	53.49500713266762
1998	53.221288515406165
1999	52.331245650661096
2000	51.38312586445366
2001	51.05189340813464
2002	50.782361308677096
2003	50.646551724137936
2004	50.93659942363112
2005	50.872093023255815
2006	50.62823355506282
2007	49.25149700598803
2008	49.113737075332345