Year	% of total
1990	16.930629039333283
1991	18.09767394569925
1992	18.03752300351376
1993	18.42910429226077
1994	18.52187602366679
1995	18.704345854442867
1996	20.68312742244457
1997	21.419171073772375
1998	21.578377510032475
1999	20.785074732942977
2000	20.604086324173167
2001	20.40874550153732
2002	19.40302199454459
2003	18.575577251572696
2004	18.534712745791495
2005	17.920383586256158
2006	17.828073990992603
2007	17.85804762223219
2008	18.497889134497438