Year	Percent
1992	38.97181
1993	36.98964
1994	38.69872
1995	29.99769
1996	25.58776
1997	25.60638
1998	29.31463
1999	32.96667
2000	37.77583
2001	36.14183
2002	35.81093
2003	35.07527
2004	35.35184
2005	37.62802
2006	39.35646
2007	37.7309
2008	40.25025
2009	38.43148
2010	40.60242
2011	37.26609
2012	36.30285
2013	33.69882
2014	33.20943
2015	30.85479
2016	31.97979
2017	31.99615