Year	Percent
1986	16.63
1987	13.58
1992	11.65
1996	15.4
2001	22.453
2002	23.129
2003	21.14
2004	20.968
2005	18.505
2007	17.806
2008	18.114
2009	18.443
2010	17.2022
2011	16.2152
2012	14.9977
2013	13.8919
2014	13.9382
2015	12.4081
2016	13.5778
2017	13.7162