Year	Percent
1973	19.54
1974	20.86
1975	5.146
1976	8.89
1977	28.68
1978	22.7
1979	16.51
1980	19.17
1981	18.97
1982	17.28
1983	19.37
1984	15.22
1985	12.96
1987	46.77
1988	67.56
1990	15.27
1991	59.07
1992	47.62
1993	50.84
1994	49.87
1995	49.87
1998	58.17
1999	48.31
2000	50.77
2001	48.52
2002	44.74
2003	39.51
2004	40.72
2005	34.49
2006	34.44
2007	32.43