Year	Percent
1991	16.964
1992	17.249
1993	17.409
1994	16.955
1995	16.973
1996	17.144
1997	17.234
1998	16.97
1999	16.883
2000	18.077
2001	17.609
2002	17.783
2003	18.64
2004	18.744
2005	18.964
2006	19.334
2007	20.303
2008	20.387
2009	20.309
2010	20.666
2011	21.027
2012	20.985
2013	21.463
2014	21.591
2015	21.42
2016	21.14
2017	21.189
2018	21.126
2019	20.975
2020	20.951
2021	20.914
2022	20.952