Year	Percent
1991	45.89
1992	45.59
1993	45.22
1994	46.42
1995	47.38
1996	48.17
1997	47.71
1998	47.22
1999	46.99
2000	47.21
2001	46.37
2002	46
2003	47.53
2004	48.77
2005	49.75
2006	49.3
2007	49.02
2008	47.1
2009	45.9
2010	42.11
2011	42.16
2012	42.21
2013	42.67
2014	41.66
2015	41.93
2016	38.9
2017	38.08
2018	37.24
2019	36.39