Year	Percent
1998	29.96
1999	30.26
2000	36.0259
2001	36.6354
2002	41.4911
2003	39.4913
2004	36.5198
2005	36.6298
2006	36.0398
2007	33.2884
2008	25.7729
2009	25.5562
2010	26.998
2011	27.2135
2012	27.0611
2013	26.5289
2014	27.0289
2015	27.5289
2016	28.9973
2017	29.4889