Year	Percent
1990	15.3
1991	15.8
1992	15.8
1993	16.3
1994	16.3
1995	16.7
1996	17
1997	17
1998	21
1999	22
2000	22
2001	22
2002	22
2003	24.6
2004	24.4
2006	25.2
2007	25.53
2008	25.28
2009	25.95