Year	Percent
1990	40.19
1991	40.86
1992	40.9
1993	41.49
1994	42
1995	42.38
1996	42.42
1997	42.35
1998	42.24
1999	42.13
2000	42.02
2001	41.93
2002	41.53
2003	40.9
2004	40.91
2005	40.89
2006	40.65
2007	42.01
2008	41.72
2009	42.53
2010	41.79
2011	41.14
2012	40.28
2013	39.25
2014	39.26
2015	39.29
2016	39.36
2017	39.41
2018	39.45
2019	39.48
2020	37.89