Year	Percent
1990	27.79
1991	23.32
1993	22.48
1995	21.66
1996	22.67
1997	22.48
1998	24.8
1999	25.55
2000	26.96
2001	25.98
2002	29.67
2003	29.37
2004	29.46
2005	25.7
2006	25.95
2007	25.96
2008	25.33
2009	24.08
2010	24.19
2011	24.08
2012	23.84
2013	24.11
2014	24.61
2015	24.96
2016	25.56
2017	25.81