Year	Percent
1991	27.505
1992	29.117
1993	28.784
1994	27.898
1995	27.081
1996	28.204
1997	26.157
1998	25.076
1999	24.516
2000	23.59
2001	23.182
2002	22.757
2003	22.531
2004	23.277
2005	21.547
2006	21.896
2007	22.716
2008	21.143
2009	21.721
2010	21.422
2011	20.176
2012	23.009
2013	25.401
2014	25.08
2015	27.066
2016	26.539
2017	26.525
2018	26.501
2019	26.479
2020	26.46
2021	26.441
2022	26.422