Year	Percent
1971	10.82
1972	6.91
1973	4.502
1974	14.36
1975	9.436
1976	10.14
1977	8.852
1978	6.286
1979	7.361
1980	3.011
1981	5.742
1982	6.151
1983	5.757
1984	4.27
1986	0.4791
1987	3.243
1988	8.616
1989	4.263
1990	4.359
1991	2.719
1992	5.226
1993	4.362
1994	7.32
1995	4.738
1996	4.84
1997	2.28
1998	3.764
1999	6.834
2000	4.64
2001	8.117
2002	3.365
2003	4.404
2004	4.103
2005	5.593
2006	4.464
2007	3.064