Year	Percent
1992	25.879
1993	28
1994	30.776
1995	28.995
1996	26.278
1997	20.1335
1998	19.5064
1999	27.9265
2000	34.2887
2001	38.0179
2002	40.9883
2003	40.2589
2004	38.9248
2005	35.7198
2006	28.297
2007	19.9725
2008	15.2455
2009	20.2099
2010	22.4177
2011	23.6384
2012	24.0836
2013	25.3812
2014	22.7168
2015	20.6556
2016	17.4448
2017	14.6064