Year	Percent
1990	0.23752
1991	0.23665
1992	0.26728
1993	0.25075
1994	0.39061
1995	0.35836
1996	0.41961
1997	0.43412
1998	0.44863
1999	0.69471
2000	0.70874
2001	0.69201
2002	0.8289
2003	0.85815
2004	0.71912
2005	0.65704
2006	0.56471
2007	0.57942
2008	0.56377
2009	0.76149
2010	0.80703
2011	0.67006
2012	0.70079
2013	0.65553
2014	0.54935
2015	0.47365
2016	0.42848
2017	0.41393