Year	Percent
1997	48.64138
1998	53.19975
1999	57.05687
2000	51.72938
2001	49.35538
2002	51.35417
2003	51.58788
2004	42.67245
2005	38.55113
2006	34.89561
2007	36.40398
2008	34.51909
2009	47.56434
2010	52.03669
2011	51.66392
2012	55.32563
2013	57.95869
2014	58.18024
2015	55.51231
2016	54.39742