Year	Percent
1991	52.89
1992	51.99
1993	50.97
1994	49.93
1995	48.89
1996	48.62
1997	48.48
1998	48.43
1999	48.46
2000	48.16
2001	47.92
2002	48.14
2003	48.39
2004	47.53
2005	46.74
2006	46.08
2007	44.68
2008	44.12
2009	43.21
2010	39.97
2011	35.22
2012	31.04
2013	29.04
2014	26.28
2015	30.13
2016	29.75
2017	29.36
2018	28.91
2019	28.34