Year	Percent
1991	31.5
1992	31.36
1993	27.95
1994	27.27
1995	26.5
1996	26.25
1997	25.59
1998	26.35
1999	25.65
2000	30.26
2001	28.12
2002	28.06
2003	26.73
2004	27.83
2005	27.65
2006	27.99
2007	27.97
2008	27.74
2009	25.44
2010	25.12
2011	25.67
2012	24.87
2013	23.34
2014	23.05
2015	23.42
2016	22.9
2017	22.83
2018	25.01
2019	26.5