Year	Percent
1991	35.58
1992	35.58
1993	35.36
1994	35.18
1995	34.96
1996	34.77
1997	34.66
1998	34.44
1999	34.38
2000	34.21
2001	34.08
2002	33.89
2003	33.79
2004	33.74
2005	33.75
2006	36.57
2007	39.1
2008	40.28
2009	39.25
2010	38.94
2011	38.91
2012	39.78
2013	40.02
2014	42.57
2015	43.59
2016	43.87
2017	44.76
2018	46.17
2019	47.12
2020	44.89