Year	Percent
1999	18.43
2000	22.05
2001	22.03
2002	21.5
2003	18.88
2004	18.23
2005	15.37
2006	14.74
2007	13.61
2008	13.96
2009	13.91
2010	14.92
2011	14.71
2012	14.16
2013	13.75
2014	13.54
2015	13.42
2016	13.07
2017	12.89
2018	12.75
2019	12.44