Year	Percent
1991	22.418
1992	21.654
1993	21.795
1994	22.455
1995	21.775
1996	22.378
1997	21.906
1998	21.923
1999	21.964
2000	21.988
2001	21.915
2002	21.886
2003	21.809
2004	20.904
2005	21.096
2006	21.104
2007	20.921
2008	20.786
2009	20.461
2010	20.835
2011	20.788
2012	20.58
2013	20.613
2014	20.497
2015	20.569
2016	20.602
2017	20.62
2018	20.639
2019	20.652
2020	20.663
2021	20.67
2022	20.674