Year	Percent
1987	14.69
1988	16.84
1989	16.59
1990	13.85
1991	12.42
1993	15.16
1995	11.93
1996	10.61
1998	8.37
1999	7.99
2000	7.39
2002	5.5
2005	3.96
2006	3.24
2007	2.53
2008	2.36
2009	3.71
2010	2.8271
2011	2.2674
2012	2.5297
2013	1.939
2014	2.0502
2015	1.7488
2016	2.794