Year	Percent
1991	35.26
1992	35.3
1993	35.31
1994	35.17
1995	35.05
1996	34.92
1997	34.6
1998	35.08
1999	35.87
2000	36.05
2001	37.03
2002	36.36
2003	34.06
2004	33.85
2005	33.84
2006	34.53
2007	35.43
2008	36.46
2009	37.57
2010	37.82
2011	38.06
2012	38.03
2013	39.59
2014	40.22
2015	41.05
2016	41.94
2017	42.82
2018	43.75
2019	45.9
2020	41.99