Year	Percent
1991	43.7
1992	42.66
1993	42.15
1994	41.67
1995	41.62
1996	40.22
1997	38.94
1998	37.77
1999	36.84
2000	34.63
2001	32.73
2002	32.82
2003	33.01
2004	31.27
2005	29.63
2006	28.14
2007	27.05
2008	25.62
2009	25.22
2010	23.98
2011	23.88
2012	23.73
2013	23.56
2014	23.47
2015	23.42
2016	23.31
2017	23.42
2018	23.56
2019	23.65