Year	% of total
1970	59.41804078705461
1971	63.935279621693866
1972	37.99371631034432
1973	55.343955134321774
1974	61.87791411206035
1975	61.96080920919636
1976	49.930725002086476
1977	35.672810317081
1978	49.919889651432605
1979	41.09954656507101
1980	41.83776906300179
1981	45.81793891369547
1982	17.471674438688606
1983	34.58647537895418
1984	49.520491903275285
1985	48.38526501782196
1986	36.447809310782894
1987	25.408608068110546
1988	49.62304564710726
1989	47.630414287096144
1990	26.175396266881133
1991	25.638646830787582
1992	26.57158459413446
1993	25.900105052048517
1994	25.46404077266721
1995	26.49260714954146
1996	26.77587119678615
1997	26.35841416329221
1998	26.843980497562196
1999	26.88165309956168
2000	26.22247107129526
2001	26.480179028132994
2002	27.400117317343415
2003	27.70716657164895
2004	29.052029419776627
2005	29.555960218518003
2006	30.504102325248112
2007	31.870737133895027
2008	33.16091098541232