Year	Percent
1986	1.6871
1987	1.4308
1988	2.6604
1989	3.2004
1990	4.054
1991	4.435
1992	4.904
1993	3.96
1994	3.558
1995	2.946
1996	2.619
1997	3.035
1998	4.336
1999	4.161
2000	3.563
2001	2.842
2002	3.383
2003	3.8154
2004	2.636
2005	1.977
2006	2.15
2007	1.33
2008	1.74
2009	2.465
2010	2.943
2011	3.35
2012	3.836
2013	4.05
2014	3.119
2015	3.397
2016	3.13
2017	2.798