Year	Percent
1971	4.61
1972	4.88
1973	4.59
1974	3.14
1975	3.58
1976	3.18
1977	2.59
1978	2.4
1980	3.19
1981	3.51
1982	3.58
1983	3.69
1984	5.21
1985	4.8
1986	4.95
1987	8.05
1988	7.65
1989	7.32
1990	7.12
1991	9.2585
1992	8.8913
1993	8.4457
1994	8.8484
1995	8.8526
1996	7.8578
1997	8.1532
1998	9.8151
1999	9.6927
2000	10.9458
2001	3.4966
2002	11.2
2003	3.33
2004	3.3478
2005	3.5414
2006	3.8761
2007	3.255
2008	3.5397
2009	3.683
2010	3.4863
2011	3.439
2012	3.3561
2013	3.2855
2014	3.5184
2016	2.6039
2017	2.4597