Year	Percent
1971	4.368
1972	8.422
1973	6.404
1974	4.604
1975	0.2349
1976	0.9871
1977	3.842
1978	8.037
1979	2.706
1980	3.381
1981	3.492
1982	2.222
1983	2.548
1984	2.359
1985	4.364
1986	3.137
1987	3.153
1988	4.56
1989	3.756
1990	5.25
1991	4.706
1992	11.43
1993	11.18
1994	13.28
1995	7.157
1996	8.096
1997	7.867
1998	10.55
1999	6.795
2000	7.719
2001	12.73
2002	31.28
2003	27.93
2004	37.17
2005	36.53
2006	42.23
2007	21.17