Year	Percent
1990	23.89
1991	23.87
1992	24.06
1993	24.04
1994	23.99
1995	23.88
1996	23.8
1997	23.63
1998	23.5
1999	23.69
2000	23.67
2001	23.51
2002	23.4
2003	23.23
2004	23.1
2005	22.93
2006	22.83
2007	22.54
2008	22.51
2009	22.43
2010	22.22
2011	22
2012	21.85
2013	21.72
2014	21.65
2015	21.6
2016	21.76
2017	21.95
2018	22.11
2019	22.18