Year	Percent
1991	48.52
1992	48.07
1993	47.27
1994	47.63
1995	46.41
1996	45.27
1997	42.26
1998	41.12
1999	38.37
2000	37.04
2001	35.46
2002	33.42
2003	30.45
2004	28.07
2005	27.44
2006	27.5
2007	28.28
2008	27.79
2009	26.3
2010	25.03
2011	24.38
2012	25.01
2013	25.43
2014	27.07
2015	28.6
2016	29.14
2017	29.7
2018	28.69
2019	28.03