Year	Percent
1995	39.24
1996	28.36
1997	34.92
1998	37.96
1999	38.02
2000	34.12
2001	28.28
2002	23.71
2003	25.58
2004	24.42
2005	26.07
2006	23.67
2007	23.76
2008	23.45
2009	18.03
2010	24.96
2011	26.08
2012	27.01
2013	28.39
2014	28.38
2015	29.15
2016	30.55
2017	31.13