Year	Percent
1991	42.42
1992	41.84
1993	41.31
1994	40.86
1995	40.28
1996	39
1997	37.92
1998	37.12
1999	36.55
2000	36.05
2001	35.35
2002	35.85
2003	35.28
2004	34.7
2005	33.42
2006	34.31
2007	32.1
2008	32.44
2009	30.7
2010	30.69
2011	30.84
2012	30.2
2013	31.34
2014	31.32
2015	32.59
2016	33.24
2017	32.42
2018	32.74
2019	31.83