Year	Percent
1991	42.98
1992	44.37
1993	43.61
1994	42.93
1995	42.39
1996	39.92
1997	39.1
1998	38.06
1999	36.71
2000	35.4
2001	33.81
2002	29.45
2003	27.53
2004	27.81
2005	24.79
2006	23.91
2007	24.14
2008	24.55
2009	24.23
2010	24.63
2011	23.83
2012	24.04
2013	23.27
2014	22.74
2015	24.92
2016	22.57
2017	24.89
2018	25.14
2019	25.12