Year	Percent
1971	12.62
1972	12.33
1973	2.924
1974	1.084
1975	2.152
1976	2.568
1977	2.873
1978	3.195
1979	2.921
1980	3.093
1981	3.578
1982	3.728
1983	7.149
1984	5.996
1985	8.757
1986	10.97
1987	7.737
1988	6.13
1989	8.59
1990	9.807
1991	8.791
1992	8.535
1993	7.988
1994	10.24
1995	10.49
1996	6.517
1997	6.93
1998	7.89
1999	12.54
2000	7.586
2001	9.526
2002	12.87
2003	13.4
2004	15.19
2005	8.759
2006	10.99
2007	8.117