Year	Percent
1991	42.6
1992	41.07
1993	38.86
1994	38.85
1995	37.77
1996	36.29
1997	35.99
1998	35.3
1999	35.56
2000	35.25
2001	33.18
2002	32.19
2003	30.83
2004	30.7
2005	29.96
2006	29.28
2007	28.93
2008	27.57
2009	25.02
2010	25.52
2011	25.53
2012	26.07
2013	26.54
2014	26.3
2015	27.28
2016	28.33
2017	29.27
2018	30.78
2019	32.3