Year	Percent
1991	32.85
1992	33.01
1993	30.27
1994	27.79
1995	26.83
1996	27.09
1997	26.53
1998	26.37
1999	22.56
2000	23.2
2001	24.34
2002	22.59
2003	21.71
2004	21.42
2005	22.81
2006	24.35
2007	26.25
2008	27.89
2009	27.32
2010	26.44
2011	24.91
2012	24.72
2013	24.36
2014	26.06
2015	26.37
2016	28.81
2017	30.19
2018	31.57
2019	32.29