Year	Percent
1991	51.2
1992	50.94
1993	50.69
1994	50.36
1995	50.01
1996	49.74
1997	49.36
1998	48.11
1999	46.64
2000	45.03
2001	44.86
2002	44.42
2003	45.04
2004	46.18
2005	46.58
2006	46.85
2007	47.84
2008	48.74
2009	48.37
2010	46.56
2011	44.73
2012	43.11
2013	41.93
2014	43.12
2015	44.04
2016	44.48
2017	45.83
2018	47.03
2019	48.07
2020	47.64