Year	Percent
1999	17.40082
2000	17.4477
2001	17.43757
2002	17.69547
2003	17.67027
2004	17.88155
2005	17.48528
2006	17.16973
2007	17.79444
2008	17.49762
2009	17.96664
2010	18.12588
2011	17.90303
2012	17.81856
2013	18.02376
2014	18.03749