Year	% of total
1970	0.3482976655375521
1971	0.3324842132672696
1972	0.3478617902907661
1973	0.3649525040289139
1974	0.38188296880081923
1975	0.3451120109561417
1976	0.3664366416042692
1977	0.3690489153409149
1978	0.3679035015803906
1979	0.377835942772304
1980	0.38994105223439934
1981	0.38013798004726546
1982	0.36171232655810165
1983	0.3407929110275718
1984	0.318276826732381
1985	0.30992738971970046
1986	0.32068330336528744
1987	0.31633950333338184
1988	0.3374213914875579
1989	0.34598670228826434
1990	0
1991	0.5847953216374269
1992	0.6493506493506493
1993	1.5267175572519083
1994	1.574803149606299
1995	2.459016393442623
1996	2.631578947368421
1997	2.5423728813559325
1998	3.7383177570093453
1999	4.2105263157894735
2000	4.2105263157894735
2001	5.05050505050505
2002	4.716981132075472
2003	5.714285714285714
2004	5.357142857142857
2005	6.0344827586206895
2006	4.651162790697675
2007	3.8461538461538463
2008	2.7210884353741496