Year	Percent
1990	0.27799
1991	0.43573
1992	0.75936
1993	0.69148
1994	0.73067
1995	0.57097
1996	0.55381
1997	0.4681
1998	0.37672
1999	0.32267
2000	0.2846
2001	0.35137
2002	0.64381
2003	0.77939
2004	0.70668
2005	0.59254
2006	0.49774
2007	0.49354
2008	0.68827
2009	1.67189
2010	2.26846
2011	2.09649
2012	1.79196
2013	1.49961
2014	1.13008
2015	0.82864
2016	0.7052
2017	0.60502