Year	Percent
1991	37.53
1992	36.34
1993	35.14
1994	34.02
1995	32.9
1996	31.76
1997	30.74
1998	29.76
1999	28.84
2000	27.34
2001	26.97
2002	26.56
2003	26.13
2004	25.65
2005	25.06
2006	24.22
2007	23.24
2008	23.68
2009	23.64
2010	24.15
2011	24.37
2012	24.65
2013	24.52
2014	24.51
2015	24.52
2016	24.5
2017	24.52
2018	24.53
2019	24.6