Year	Percent
1971	0.9318
1972	0.7459
1973	4.869
1974	9.009
1975	10.58
1976	12.93
1977	12.41
1978	14.32
1979	12.15
1980	10.52
1981	11.58
1982	11.97
1983	12.25
1984	9.969
1985	5.638
1986	3.453
1987	6.81
1988	6.772
1989	4.897
1990	4.357
1991	5.036
1992	4.046
1993	3.688
1994	5.342
1995	6.233
1996	5.039
1997	4.471
1998	6.085
1999	5.311
2000	5.241
2001	7.308
2002	8.504
2003	6.2
2004	8.161
2005	7.551
2006	5.744
2007	3.315