Year	Percent
1971	1.351
1972	0.376
1973	1.668
1974	21.02
1975	10.55
1976	9.494
1977	2.638
1978	3.574
1979	4.112
1980	2.239
1981	2.563
1982	4.073
1983	4.27
1984	2.669
1985	3.679
1986	2.592
1987	3.112
1988	3.093
1989	1.459
1990	5.643
1991	0.99
1992	19.35
1993	26.45
1994	0.4688
1995	16.78
1996	21.44
1997	31.7
1998	17.62
1999	15.81
2000	11.71
2001	13.56
2002	11.72
2003	11.72
2004	14.1
2005	21.4
2006	7.894
2007	14.2