Year	Percent
1990	58.44
1991	58.56
1992	58.6
1993	58.6
1994	58.51
1995	58.13
1996	57.94
1997	57.88
1998	57.72
1999	56.8
2000	55.86
2001	54.91
2002	53.93
2003	52.93
2004	51.89
2005	50.84
2006	49.86
2007	48.87
2008	47.85
2009	46.81
2010	45.76
2011	44.77
2012	43.76
2013	42.73
2014	41.68
2015	40.6
2016	39.54
2017	37.41
2018	37.16
2019	36.9