Year	Percent
1971	0.7217
1973	1.576
1974	0.9171
1975	0.801
1976	0.6655
1977	0.8241
1978	0.5525
1979	0.5785
1980	0.4779
1981	0.7076
1982	0.2147
1983	0.2788
1984	0.4508
1985	0.6008
1986	2.721
1987	0.06701
1988	0.4709
1989	4.215
1990	0.543
1991	1.808
1992	1.786
1993	1.038
1994	7.632
1995	10.85
1996	9.131
1997	13.44
1998	20.43
1999	20.68
2000	29.87
2001	20.27
2002	31.51
2003	26.21
2004	27.38
2005	25.55
2006	28.87
2007	28.71