Year	Percent
1998	21.32
1999	21.06
2000	25.6632
2001	26.519
2002	27.4945
2003	27.2082
2004	24.5212
2005	23.6875
2006	22.7174
2007	21.638
2008	19.7078
2009	21.9039
2010	22.8443
2011	22.5653
2012	22.8459
2013	22.9574
2014	23.1482
2015	23.2034
2016	24.5491
2017	25.5367