Year	Percent
1990	52.08
1991	51.98
1992	51.93
1993	51.45
1994	51.74
1995	50.5
1996	51.06
1997	51.66
1998	51.6
1999	51.95
2000	52.43
2001	52.32
2002	52.32
2003	52.8
2004	53.29
2005	52.96
2006	52.59
2007	52.67
2008	52.61
2009	53.17
2010	53.61
2011	53.63
2012	53.95
2013	54.27
2014	54.19
2015	55.08
2016	54.85
2017	54.64
2018	54.43
2019	54.5