Year	Percent
1991	42.21
1992	41.89
1993	41.49
1994	41
1995	40.37
1996	40.1
1997	39.7
1998	39.17
1999	38.61
2000	38.12
2001	37.81
2002	37.46
2003	36.52
2004	35.6
2005	34.73
2006	34.05
2007	33.27
2008	32.39
2009	31.29
2010	30.35
2011	29.44
2012	28.75
2013	28.03
2014	27.31
2015	26.54
2016	26.45
2017	26.31
2018	26.12
2019	25.87