Year	Percent
1991	47.11
1992	47.05
1993	46.96
1994	46.76
1995	46.59
1996	46.72
1997	46.69
1998	46.71
1999	46.79
2000	46.74
2001	46.75
2002	46.52
2003	45.91
2004	44.62
2005	44.91
2006	45.17
2007	46
2008	46.32
2009	45.97
2010	46.57
2011	47.6
2012	48.82
2013	50.21
2014	51.27
2015	51.62
2016	52.58
2017	53.47
2018	54.9
2019	55.89
2020	55.87