Year	Percent
1990	51.8
1991	52.4
1992	54.4
1993	54.5
1994	50.3
1995	54
1996	53.2
1997	50.8
1998	22.1
1999	21.3
2000	20.1
2001	19.7
2002	24.8
2003	23.4
2004	22.14
2005	22.67
2007	28.6