Year	% of total
1970	46.57771181672605
1971	43.881175341123964
1972	37.79323342641091
1973	36.51008402006903
1974	38.26997338454633
1975	41.73893907825652
1976	41.1499667328324
1977	38.216820340831184
1978	35.64306851869167
1979	33.54334096802534
1980	31.769488412068224
1981	34.777406399112984
1982	38.1655875990075
1983	41.04518018299673
1984	43.5462542832758
1985	45.669887885336436
1986	46.93347459874924
1987	49.72183984372839
1988	49.102931024301725
1989	50.62451277632112
1990	78.29099307159353
1991	78.58719646799118
1992	78.46481876332622
1993	76.99115044247787
1994	74.7072599531616
1995	71.61125319693095
1996	71.60493827160494
1997	72.55813953488372
1998	72.58426966292136
1999	71.81208053691275
2000	72.37687366167023
2001	72.14137214137214
2002	71.89409368635438
2003	72.02380952380952
2004	72.08413001912047
2005	70.23809523809523
2006	69.41176470588235
2007	69.12878787878788
2008	63.655913978494624