Year	% of total
1990	33.14552134914688
1991	32.95929075101036
1992	32.009086326927424
1993	31.691491227406328
1994	30.969598630952024
1995	30.727692389630796
1996	31.109206953548792
1997	31.318178595489726
1998	31.301106310133815
1999	31.422681794164507
2000	32.03562748295045
2001	32.845698207263915
2002	33.37474145559885
2003	34.59584176629642
2004	35.13569773862239
2005	35.5916262815658
2006	36.20315968320171
2007	36.8503235577346
2008	37.381096946807915