Year	Percent
1989	21.69
1997	17.34
1999	16.56
2000	16.1
2001	15.56
2002	15.73
2003	16.18
2005	15.1601
2006	15.1389
2007	15.1526
2008	15.9384
2009	18.7703
2010	18.9403
2011	27.3726
2012	25.6059
2013	23.0021
2015	22.2323
2016	23.1232
2017	22.7757