Year	Percent
1990	31.35
1991	31.35
1992	33.09
1993	34.95
1994	33.23
1995	31.12
1996	30.3
1997	30.74
1998	31.91
1999	30.85
2000	29.43
2001	28.65
2002	29.55
2003	29.42
2004	29.16
2005	29.15
2006	29.04
2007	28.44
2008	28.51
2009	27.8
2010	27.53
2011	26.83
2012	27.2
2013	27.02
2014	26.95
2015	27.77
2016	27.22
2017	27.01
2018	27.25
2019	27.12