Year	Percent
1991	45.3
1992	45.16
1993	45.04
1994	45.03
1995	45.12
1996	45.15
1997	45.28
1998	45.48
1999	45.7
2000	45.98
2001	46.27
2002	46.56
2003	46.91
2004	47.3
2005	47.72
2006	47.94
2007	48.15
2008	48.34
2009	48.32
2010	48.45
2011	48.53
2012	48.59
2013	48.64
2014	48.73
2015	48.82
2016	48.84
2017	48.92
2018	49
2019	49.05
2020	46.95