Year	Percent
1973	29.64
1974	13.51
1975	14.07
1976	20.18
1977	15.14
1978	1.537
1979	8.613
1980	3.658
1981	3.003
1982	4.802
1983	4.968
1984	4.47
1985	3.525
1986	7.857
1988	6.176
1989	5.657
1990	2.051
1991	6.763
1992	3.642
1993	5.846
1994	5.25
1995	10.4
1996	5.289
1997	11.09
1998	9.563
1999	13.96
2000	13.43
2001	11.98
2002	14.34
2003	14.59
2004	24.26
2005	10.26
2006	8.439
2007	7.61