Year	Percent
1991	54.49
1992	54.48
1993	54.21
1994	53.96
1995	53.73
1996	53.5
1997	53.29
1998	53.06
1999	52.8
2000	52.57
2001	52.32
2002	51.99
2003	51.94
2004	52.8
2005	53.52
2006	53.26
2007	53
2008	52.69
2009	52.13
2010	52.17
2011	52.26
2012	52.36
2013	53.41
2014	52.97
2015	52.48
2016	51.93
2017	51.3
2018	50.59
2019	49.82