Year	Percent
1991	43.06
1992	43.22
1993	43.37
1994	43.69
1995	43.89
1996	43.93
1997	43.74
1998	47.9
1999	47.81
2000	47.77
2001	48.37
2002	47.7
2003	47.06
2004	49.02
2005	48.78
2006	50.61
2007	47.97
2008	46.85
2009	43.35
2010	41.22
2011	38.98
2012	39.84
2013	38.27
2014	37.5
2015	40
2016	41.03
2017	42.86
2018	41.84
2019	41.65