Year	Percent
1991	38.75
1992	42.53
1993	35.25
1994	36.72
1995	33.59
1996	33.7
1997	33.97
1998	32.76
1999	31.99
2000	26.57
2001	22.62
2002	26.02
2003	24.07
2004	20.78
2005	21.33
2006	23.73
2007	24.78
2008	25.92
2009	20.65
2010	18.35
2011	19.08
2012	21.45
2013	24.35
2014	27.39
2015	28.42
2016	30.99
2017	31.5
2018	33.43
2019	33.15