Year	% of total
1970	81.98527017163596
1971	81.09245968052028
1972	79.60914246331564
1973	79.74763899478178
1974	81.3743985370976
1975	77.74147719283495
1976	78.14419506843227
1977	79.9546178256754
1978	80.1764899730123
1979	79.18736766039991
1980	78.85912648057084
1981	78.89201458206345
1982	76.70596675635535
1983	76.81438477568983
1984	78.04534938429067
1985	77.54846308654862
1986	76.50299967876086
1987	73.42910238377553
1988	75.25485363440858
1989	72.57724293809402
1990	29.130434782608695
1991	26.49478880965442
1992	26.456440406199892
1993	26.395409494001044
1994	27.334024896265557
1995	26.810477657935284
1996	27.065868263473053
1997	30.774503084304317
1998	31.48464163822526
1999	40.140845070422536
2000	49.544863459037714
2001	47.56898817345598
2002	47.63729246487867
2003	48.661800486618006
2004	45.17766497461929
2005	48.13084112149533
2006	47.61904761904761
2007	45.8628841607565
2008	49.12663755458515