Year	Percent
1971	0.9164
1972	1.018
1973	0.8602
1974	1.299
1975	0.6035
1976	1.014
1977	1.038
1978	1.253
1979	0.6645
1980	3.938
1981	0.1691
1982	1.588
1983	0.3972
1984	0.3114
1985	5.974
1986	4.025
1987	4.873
1988	4.519
1989	7.559
1990	7.355
1991	8.244
1992	8.526
1993	9.819
1994	8.58
1995	7.817
1996	8.836
1997	8.649
1998	9.555
1999	8.485
2000	6.672
2001	5.846
2002	5.001
2003	3.975
2004	3.072
2005	3.906
2006	4.371
2007	4.447
2008	4.238
2009	4.16
2010	3.649