Year	Percent
1990	31.75
1991	31.97
1992	31.89
1993	30.65
1994	31.58
1995	32.08
1996	32.85
1997	33.71
1998	34.09
1999	33.35
2000	32.61
2001	31.35
2002	30.1
2003	30.27
2004	30.42
2005	28.76
2006	27.15
2007	25.58
2008	25.73
2009	24.24
2010	23.31
2011	22.79
2012	23.38
2013	23.99
2014	22.82
2015	24.7
2016	24.68
2017	24.69
2018	24.7
2019	24.66