Year	Percent
1991	34.49
1992	33.72
1993	32.83
1994	32.02
1995	31.34
1996	30.92
1997	30.65
1998	30.52
1999	30.45
2000	30.43
2001	29.59
2002	28.31
2003	28.86
2004	28.94
2005	28.84
2006	28.55
2007	28.94
2008	29.28
2009	29.3
2010	29.45
2011	29.66
2012	29.83
2013	29.61
2014	29.36
2015	29.04
2016	28.69
2017	28.3
2018	27.87
2019	27.44