Year	Percent
1991	20.02
1992	20.942
1993	21.398
1994	21.398
1995	21.741
1996	21.973
1997	21.574
1998	21.911
1999	21.699
2000	20.115
2001	20.177
2002	19.049
2003	18.278
2004	18.893
2005	20.479
2006	21.082
2007	21.005
2008	21.442
2009	21.091
2010	21.828
2011	21.624
2012	22.129
2013	22.408
2014	22.317
2015	22.564
2016	22.958
2017	21.469
2018	21.48
2019	21.882
2020	22.094
2021	22.317
2022	22.55