Year	Percent
1976	37.24
1977	37.9
1978	35.72
1979	31.25
1981	36.12
1982	38.74
1983	47.3
1984	40.59
1985	41.86
1986	42.7
1987	41.03
1988	34.97
1990	31.33
1991	34.1
1992	34.09
1993	30.5
1995	26.42
1996	27.78
1997	27.14
1998	24.88
1999	22.69
2000	20.5
2002	23.27
2003	23.22
2004	21.23
2005	23.26
2006	22.34
2007	22.16
2008	24.53