1983 10.9%
1984 15.2%
1985 13.5%
1986 8.8%
1987 11.6%
1988 11.3%
1989 4.1%
1990 3.8%
1991 9.2%
1992 14.2%
1993 14.0%
1994 13.1%
1995 10.9%
1996 10.0%
1997 9.3%
1998 7.8%
1999 7.6%
2000 8.4%
2001 8.3%
2002 9.1%
2003 10.0%
2004 10.1%
2005 10.4%
2006 10.7%
2007 11.9 %