Year	% of total
1970	75.60051601990362
1971	75.40841172755376
1972	75.71204359467103
1973	75.65085442090412
1974	75.83217826516625
1975	76.03043015171878
1976	76.20180160320879
1977	76.4250384197135
1978	76.49668644046763
1979	76.61532400892341
1980	76.63688825237868
1981	76.68825032594525
1982	76.5966330727213
1983	76.65302736800278
1984	76.92310824172628
1985	76.98514019774447
1986	77.01901776584256
1987	76.98706331776994
1988	76.96572839595508
1989	77.0589937491804
1990	84.688995215311
1991	83.9622641509434
1992	83.29411764705881
1993	82.48847926267281
1994	82.52212389380531
1995	82.34042553191489
1996	81.44329896907216
1997	80.36072144288578
1998	79.53667953667953
1999	78.03468208092485
2000	76.99619771863118
2001	76.93761814744802
2002	76.30057803468208
2003	76.01547388781431
2004	76.32575757575758
2005	76.27118644067797
2006	75.09090909090908
2007	73.8898756660746
2008	73.25383304940375