Year	Percent
1991	30.38
1992	29.93
1993	28.34
1994	27.55
1995	27.17
1996	26.12
1997	25.49
1998	25.83
1999	25.22
2000	25.29
2001	25.43
2002	25.55
2003	25.71
2004	25.96
2005	26.29
2006	26.75
2007	27.28
2008	23.72
2009	19.72
2010	21.45
2011	23.83
2012	25.47
2013	25.35
2014	24.31
2015	27.52
2016	22.96
2017	22.47
2018	23.57
2019	22.52