Year	Percent
1990	46.75
1991	46.61
1992	46.67
1993	46.62
1994	46.58
1995	46.53
1996	46.53
1997	46.51
1998	46.54
1999	46.85
2000	47.01
2001	47.04
2002	47.17
2003	47.28
2004	47.48
2005	47.68
2006	47.95
2007	48.13
2008	48.59
2009	49.05
2010	49.45
2011	49.59
2012	49.87
2013	50.26
2014	50.77
2015	51.34
2016	51.82
2017	52.27
2018	52.65
2019	52.9
2020	52.04