Year	Percent
1991	48.6
1992	48.33
1993	47
1994	47.17
1995	46.44
1996	45.7
1997	44.65
1998	42.52
1999	42.92
2000	42.99
2001	42.21
2002	40.29
2003	38.76
2004	38.87
2005	35.36
2006	36.69
2007	39.08
2008	40.21
2009	40.02
2010	40.02
2011	39.26
2012	41.08
2013	40.19
2014	39.29
2015	38.03
2016	38.61
2017	40.29
2018	39.68
2019	41.48