Year	Percent
1991	48.71
1992	39.69
1993	34.65
1994	32.06
1995	29.67
1996	27.73
1997	31.19
1998	32.59
1999	35.01
2000	35.22
2001	36.34
2002	35.65
2003	36.06
2004	36.38
2005	40.6
2006	42.29
2007	44.79
2008	44.94
2009	39.64
2010	38.79
2011	40.3
2012	41.72
2013	41.45
2014	41.5
2015	40.68
2016	41.85
2017	42.69
2018	44.2
2019	44.69