Year	Percent
1976	15.78
1977	14.96
1978	12.91
1979	11.82
1981	14.29
1982	16.36
1983	19.37
1984	17.56
1985	18.21
1986	16.13
1987	14.55
1988	12.97
1990	12.95
1991	14.64
1992	14.89
1993	15.03
1995	12.43
1996	11.71
1997	11.82
1998	11.81
1999	10.18
2000	8.86
2002	10.49
2003	10.46
2004	9.06
2005	9.89
2006	9.91
2007	9.86
2008	10.57