Year	Percent
1986	4.7778
1987	3.9777
1988	2.9206
1989	2.6085
1990	2.3751
1991	1.9043
1992	2.349
1993	3.5527
1994	4.8374
1995	5.3259
1996	5.1762
1997	5.0275
1998	3.1824
1999	3.7444
2000	2.7236
2001	2.5062
2002	3.2658
2003	4.7706
2004	4.8706
2005	6.1453
2006	5.8308
2007	6.1011
2008	5.971
2009	8.4702
2010	9.2661
2011	11.5548
2012	14.6721
2013	15.4243
2014	12.0207
2015	10.8217
2016	9.6551
2017	7.2809