Year	Percent
1976	18.2
1977	17.13
1978	14.8
1979	14.2
1981	16.79
1982	19.8
1983	23.11
1984	20.87
1985	21.71
1986	19.73
1987	17.53
1988	15.7
1990	15.67
1991	16.88
1992	17.42
1993	17.44
1995	14.72
1996	12.94
1997	12.98
1998	13
1999	11.67
2000	10.52
2002	12.11
2003	11.39
2004	10.2
2005	10.56
2006	10
2007	10.7
2008	11.69