Year	% of total
1970	52.766638453942726
1971	53.448766674718854
1972	53.325211199846045
1973	52.67011215519853
1974	52.24318571121653
1975	52.72746232115182
1976	52.135266119774904
1977	52.00381109371136
1978	52.526789953017314
1979	53.10011293334729
1980	55.51399501108648
1981	55.86897905759163
1982	57.341597793091225
1983	58.986809015421116
1984	59.473389306088244
1985	61.30162941670435
1986	61.88798333280119
1987	62.43332544092267
1988	64.44645408684794
1989	62.01196166328258
1990	82.62921878687752
1991	83.37141406448337
1992	84.01350971010415
1993	84.11424903722721
1994	85.17361111111111
1995	85.88507520246819
1996	83.34071776694726
1997	82.4672390420244
1998	82.17568947906027
1999	80.92140921409214
2000	79.00492072170586
2001	79.4858061060525
2002	77.93068297655454
2003	76.03260869565217
2004	77.10306406685237
2005	75.14029180695847
2006	74.86187845303867
2007	72.25705329153605
2008	76.25