Year	% of total
1970	40.70959693909312
1971	40.14056634594589
1972	40.54242212172619
1973	40.31358487897607
1974	38.38561793131811
1975	40.93379497138184
1976	42.33431394972489
1977	42.11183408630495
1978	43.263611497931954
1979	44.79220547770018
1980	45.293595627957615
1981	46.37604992151909
1982	46.222411362485225
1983	45.763274994163346
1984	45.42836275591271
1985	45.47616944012132
1986	46.41101615495357
1987	46.961340212497596
1988	47.56403700637231
1989	48.58369522354729
1990	59.42763695829927
1991	59.733723006981656
1992	57.00840336134454
1993	56.60597962251545
1994	56.60190977938755
1995	56.560427115353505
1996	56.36053366428793
1997	56.41986879100281
1998	63.523225241016654
1999	70.77102349970869
2000	72.14213197969544
2001	71.08673978065802
2002	72.36044323646247
2003	71.93717277486911
2004	76.523851590106
2005	75.9718117754035
2006	76.91772885283893
2007	78.12854871678401
2008	78.85985748218528