Year	Percent
1990	41.06
1991	41.03
1992	40.92
1993	40.94
1994	41.03
1995	40.97
1996	41.13
1997	40.82
1998	40.45
1999	40.29
2000	40.8
2001	37.08
2002	36.3
2003	39.09
2004	38.5
2005	38.85
2006	38.74
2007	39.86
2008	39.12
2009	39.13
2010	39.49
2011	40.83
2012	41.18
2013	41.32
2014	41.71
2015	43.67
2016	43.61
2017	43.98
2018	43.52
2019	44.39
2020	42.77