Year	% of total
1990	22.267999070851015
1991	23.079521251581824
1992	22.848759638553403
1993	22.350016695012588
1994	21.88801406165587
1995	22.26132419637544
1996	23.791991751067624
1997	24.255045712595198
1998	24.035226742659155
1999	24.60519688800233
2000	25.740667082505144
2001	27.30851012379194
2002	27.301656960492597
2003	28.363505138922886
2004	28.745902590858694
2005	28.944396864431077
2006	29.870058495092927
2007	29.787612530933355
2008	29.969602316309786