Year	Percent
1971	0.654
1972	1.058
1973	4.508
1974	2.166
1975	1.608
1976	0.3014
1977	3.881
1978	1.761
1979	1.966
1980	2.418
1981	2.911
1982	2.063
1983	3.226
1984	3.938
1985	7.775
1986	6.199
1987	3.816
1988	4.21
1989	4.369
1990	6.892
1991	3.512
1992	6.68
1993	7.838
1994	8.568
1995	9.15
1996	10.83
1997	16.48
1998	10.29
1999	9.99
2000	15.42
2001	10.82
2002	16.98
2003	13.94
2004	8.301
2005	9.485
2006	12.32
2007	11.97