Year	Percent
1991	41.82
1992	40.93
1993	39.74
1994	38.25
1995	36.71
1996	35.54
1997	34.47
1998	33.5
1999	32.65
2000	32.01
2001	31.33
2002	30.73
2003	30.22
2004	31.15
2005	31.61
2006	31.69
2007	30.5
2008	29.15
2009	27.86
2010	26.93
2011	26.45
2012	26.04
2013	25.52
2014	24.84
2015	24.05
2016	23.61
2017	23.25
2018	22.91
2019	23.21