Year	Percent
1991	49.94
1992	49.97
1993	49.07
1994	48.21
1995	47.38
1996	46.56
1997	45.75
1998	45.69
1999	43.81
2000	41.79
2001	41.36
2002	41.9
2003	43.37
2004	44.92
2005	45.3
2006	47.64
2007	50.09
2008	52.03
2009	50.62
2010	47.91
2011	46.62
2012	46.56
2013	46.89
2014	47.96
2015	49.22
2016	49.4
2017	52.04
2018	52.57
2019	54.35
2020	51.68