Year	Percent
1998	18.11438
1999	16.65471
2000	17.29084
2001	16.14684
2002	16.3678
2003	15.91981
2004	15.99791
2005	19.50424
2006	16.6995
2007	13.91453
2008	15.69306
2009	16.7302
2010	17.91876
2011	18.0746
2012	18.96632
2013	19.5612