Year	% of total
1990	6.549500155564115
1991	7.109685139554148
1992	7.485657972974664
1993	7.970368119466148
1994	8.088150900357025
1995	8.348258633152827
1996	8.6534542605884
1997	8.770213965989901
1998	8.865557170913668
1999	8.933343786311257
2000	8.379307708492496
2001	8.30335584083686
2002	8.442633786616518
2003	8.565022065107376
2004	8.382895618977713
2005	8.231119356997127
2006	8.226106660126996
2007	8.172679813904528
2008	8.50379605997229