Year	Percent
1999	8.15
2000	9.34
2001	9.14
2002	11.51
2003	12.52
2004	13.36
2005	14.07
2006	14.69
2007	14.22
2008	13.78
2009	15.94
2010	17.38
2011	19.21
2012	21.28
2013	20.73
2014	21.58
2015	21.38
2016	21.1
2017	21.3