Year	Percent
1973	20.98
1974	48.52
1975	42.22
1976	42.39
1977	40.14
1978	48.83
1979	74.86
1980	71.25
1981	58.55
1982	56.76
1983	60.53
1984	57.09
1985	34.48
1986	32.19
1988	30.75
1989	30.1
1990	55.69
1991	14.52
1992	51.15
1993	29.28
1994	48.64
1995	8.098
1996	20.64
1997	17.19
1998	21.17
1999	9.266
2000	8.612
2001	11.6
2002	12.61
2003	5.565
2004	10.36
2005	10.66
2006	12.59
2007	13.56