Year	Percent
1997	37.94443
1998	21.38928
2002	20.02783
2003	20.84973
2004	19.58362
2005	18.49543
2006	17.75926
2007	17.85465
2008	17.57616
2009	20.91804
2010	20.7242
2011	19.57995
2012	19.23363
2013	19.95669
2014	20.02727