Year	Percent
1990	22.79
1991	22.82
1992	22.84
1993	22.85
1994	22.85
1995	22.75
1996	22.67
1997	24.1
1998	21.96
1999	20.51
2000	22.63
2001	23.23
2002	23.84
2003	24.47
2004	25.11
2005	25.77
2006	26.45
2007	27.15
2008	27.86
2009	28.58
2010	27.34
2011	27.73
2012	28.25
2013	26.63
2014	25.67
2015	25.4
2016	24.89
2017	24.72
2018	25.08
2019	24.34