Year	Percent
1990	42.57
1991	42.39
1992	42.45
1993	42.51
1994	42.42
1995	42.49
1996	42.47
1997	42.52
1998	42.54
1999	42.45
2000	39.92
2001	37.6
2002	38.09
2003	38.62
2004	39.19
2005	39.79
2006	38.15
2007	37.69
2008	38.35
2009	41.31
2010	39.84
2011	39.23
2012	36.14
2013	40.24
2014	39.25
2015	39.88
2016	36.4
2017	42.82
2018	41.45
2019	41.46