Year	Percent
1991	41.43
1992	39.88
1993	35.88
1994	33.93
1995	27.7
1996	28.96
1997	30.97
1998	32.78
1999	31.57
2000	30.96
2001	29.04
2002	26.99
2003	30.92
2004	32.82
2005	33.09
2006	34.73
2007	35.11
2008	34.58
2009	33.64
2010	32.82
2011	33.08
2012	32.85
2013	32.04
2014	31.15
2015	30.75
2016	30.17
2017	29.59
2018	29.59
2019	28.46