Year	Percent
1991	28.856
1992	28.746
1993	26.891
1994	25.837
1995	24.773
1996	25.146
1997	24.665
1998	25.521
1999	24.934
2000	24.772
2001	25.503
2002	24.532
2003	23.379
2004	22.629
2005	21.173
2006	20.849
2007	21.077
2008	20.913
2009	19.352
2010	19.771
2011	19.835
2012	19.063
2013	19.052
2014	19.153
2015	18.939
2016	19.16
2017	18.858
2018	18.465
2019	18.191
2020	17.898
2021	17.595
2022	17.281