Year	Percent
1983	5.8052
1984	5.9815
1985	5.6432
1986	5.0422
1987	5.1229
1988	4.8437
1989	4.5774
1990	4.2505
1991	4.7577
1992	4.9119
1993	5.6708
1994	6.0104
1995	6.2003
1996	6.0155
1997	6.2263
1998	7.11
1999	7.6922
2000	7.4401
2001	6.9146
2002	6.4322
2003	6.0306
2004	6.4136
2005	6.2223
2006	5.6886
2007	5.2403
2008	5.1265
2009	6.9662
2010	10.0338
2011	15.1182
2012	21.5374
2013	24.4734
2014	23.5961
2015	21.7173
2016	19.8557
2017	17.8172