Year	Percent
1990	61.57
1991	61.16
1992	60.76
1993	60.39
1994	59.94
1995	59.51
1996	59.23
1997	58.96
1998	58.7
1999	58.45
2000	57.39
2001	56.32
2002	55.25
2003	54.19
2004	53.1
2005	52
2006	50.94
2007	49.87
2008	48.79
2009	47.69
2010	46.57
2011	45.63
2012	44.7
2013	43.77
2014	43.58
2015	43.32
2016	43.18
2017	43.14
2018	43.03
2019	42.86