Year	Percent
1991	42.27
1992	41.84
1993	41.33
1994	40.74
1995	41.22
1996	40.2
1997	36.01
1998	34.41
1999	36.76
2000	37.66
2001	35.81
2002	34.42
2003	33.23
2004	32.85
2005	35.05
2006	37.62
2007	39.39
2008	40.25
2009	36.81
2010	34.37
2011	32.46
2012	32.47
2013	29.24
2014	30.31
2015	31.18
2016	31.98
2017	32.75
2018	36.65
2019	38.17