Year	Percent
1990	27.35
1991	27.76
1992	27.97
1993	27.83
1994	27.52
1995	27.62
1996	27.52
1997	27.84
1998	27.76
1999	27.26
2000	27.42
2001	27.59
2002	26.92
2003	26.34
2004	27.37
2005	27.97
2006	27.4
2007	26.83
2008	26.26
2009	26.2
2010	25.09
2011	24.91
2012	24.64
2013	24.6
2014	24.29
2015	23.91
2016	22.78
2017	21.89
2018	20.87
2019	18.99