Year	Percent
1971	3.557
1972	20.95
1973	1.285
1974	2.603
1975	1.242
1976	1.161
1977	1.034
1978	0.8917
1979	1.006
1980	0.302
1981	0.1025
1985	1.192
1986	11.86
1987	0.485
1988	2.727
1989	5.89
1990	4.739
1991	3.991
1992	4.179
1993	5.177
1994	4.855
1995	3.68
1996	4.458
1997	4.407
1998	4.372
1999	4.216
2000	2.968
2001	3.453
2002	1.037
2003	1.337
2004	1.011
2005	1.483
2006	1.598
2007	2.537