Year	Percent
1990	18.08
1991	18.02
1992	17.75
1993	17.71
1994	16.71
1995	19.82
1996	19.64
1997	19.47
1998	19.53
1999	19.6
2000	20.19
2001	20.81
2002	21.47
2003	21.97
2004	22.77
2005	23.13
2006	24.08
2007	22.55
2008	25.42
2009	25.33
2010	25.23
2011	25.15
2012	25.06
2013	27.25
2014	27.17
2015	25.56
2016	27.88
2017	27.12
2018	28.69
2019	29.36