Year	Percent
1991	43.79
1992	44.84
1993	44.46
1994	47.07
1995	47.13
1996	47.11
1997	47
1998	46.76
1999	44.14
2000	41.58
2001	39.91
2002	34.89
2003	33.08
2004	35.6
2005	37.86
2006	39.31
2007	42.13
2008	43.02
2009	43.52
2010	43.92
2011	45.01
2012	43.81
2013	43.75
2014	43.31
2015	40.4
2016	38.85
2017	37.14
2018	36.13
2019	34.51