Year	% of total
1970	43.48982846997508
1971	43.81180296278455
1972	43.11045097822483
1973	41.74192255152342
1974	41.693121525817915
1975	42.41553822134469
1976	42.161169620488074
1977	42.283803769376846
1978	43.12835501147666
1979	42.816061753175894
1980	45.450032350544554
1981	44.76245154245155
1982	46.13922764576363
1983	46.736505996703244
1984	47.741539854609655
1985	47.70223323697832
1986	49.40564697170245
1987	49.704282603507046
1988	49.94872153374828
1989	50.74837537035851
1990	71.41104294478528
1991	70.2572347266881
1992	66.55629139072848
1993	66.91042047531994
1994	64.60176991150442
1995	61.97183098591549
1996	63.03236797274276
1997	60.854092526690394
1998	58.992805755395686
1999	60.451977401129945
2000	62.43194192377496
2001	64.50511945392492
2002	59.918200408997954
2003	60.040160642570285
2004	58.84615384615385
2005	58.47953216374269
2006	59.199999999999996
2007	61.63021868787276
2008	61.74089068825911