Year	Percent
1971	1.693
1972	0.3263
1973	0.8603
1974	0.585
1975	2.415
1976	2.69
1977	1.724
1978	0.9702
1979	3.425
1980	2.21
1981	0.6959
1982	1.779
1983	11.73
1984	4.132
1985	2.601
1986	2.75
1987	2.226
1988	3.877
1989	1.731
1990	1.288
1991	0.9882
1992	4.649
1993	2.676
1994	3.107
1995	2.663
1996	2.815
1997	4.028
1998	3.016
1999	3.306
2000	3.023
2001	2.813
2002	3.125
2003	4.788
2004	4.556
2005	5.898
2006	7.399
2007	6.697