Year	Percent
1991	45.98
1992	46.3
1993	46.56
1994	46.87
1995	47.11
1996	47.69
1997	48.01
1998	48.41
1999	48.39
2000	48.85
2001	49.54
2002	49.95
2003	50.52
2004	50.84
2005	51.46
2006	52.02
2007	53
2008	53.53
2009	54.52
2010	53.62
2011	53.13
2012	52.83
2013	52.75
2014	52.88
2015	52.89
2016	52.93
2017	52.95
2018	52.81
2019	52.62
2020	48.35