Year	Percent
1992	30.081
1993	32.48
1994	34.651
1995	33.791
1996	31.24
1997	26.1008
1998	23.491
1999	31.5654
2000	37.2492
2001	40.5893
2002	42.3718
2003	42.7697
2004	41.5232
2005	38.3231
2006	31.6294
2007	23.7958
2008	19.8586
2009	21.225
2010	25.4278
2011	28.8249
2012	29.9523
2013	30.0868
2014	25.5165
2015	20.9333
2016	17.9692
2017	15.1307