Year	Percent
1971	47.04
1972	46
1973	12.03
1974	15.01
1975	8.7
1976	11.48
1977	14.56
1978	19.49
1979	14.74
1980	13.05
1981	12.76
1982	11.9
1983	12.35
1984	11.36
1985	16.65
1986	4.996
1987	13.36
1988	12.64
1989	16.79
1990	16.19
1991	11.73
1992	13.21
1993	15.23
1994	9.958
1995	10.21
1996	7.455
1998	8.412
1999	6.607
2000	8.004
2001	7.128
2002	7.421
2003	6.757
2004	6.407
2005	6.103
2006	7.176
2007	7.09