Year	Percent
1972	10.44
1975	3.063
1976	2.326
1977	3.745
1978	2.595
1979	5.23
1980	5.154
1981	8.575
1982	13.85
1983	8.567
1984	13.45
1985	4.348
1986	4.902
1987	3.445
1988	4.174
1989	2.918
1990	2.203
1991	12.1
1992	5.614
1993	14.96
1994	8.134
1995	8.827
1996	13.28
1997	8.311
1998	13.06
1999	11.92
2000	9.661
2001	18
2002	20.21
2003	11.45
2004	10.69
2005	13.24
2006	14.35
2007	15.84