Year	Percent
1989	16.13
1997	15.94
1999	15.21
2000	14.94
2001	14.4
2002	14.55
2003	14.51
2004	14.23
2005	12.87
2006	12.51
2007	12.36
2008	12.44
2009	13.29
2010	13.05
2011	18.33
2012	17.63
2013	15.93
2015	15.16
2016	15.56
2017	15.33
2018	15.46
2019	15.13