Year	Percent
1991	45.35
1992	44.45
1993	50.67
1994	49.91
1995	49.32
1996	51.74
1997	46.88
1998	43.51
1999	40.11
2000	38.64
2001	39.9
2002	34.53
2003	30.65
2004	32.19
2005	35.28
2006	37.37
2007	42.31
2008	43.96
2009	45.34
2010	46.63
2011	45.89
2012	43.27
2013	43.99
2014	43.56
2015	42.7
2016	42.33
2017	42.84
2018	43.71
2019	44.31