Year	Percent
1991	16.509
1992	16.14
1993	14.932
1994	13.957
1995	13.715
1996	14.138
1997	14.02
1998	14.362
1999	13.647
2000	14.863
2001	12.347
2002	12.515
2003	12.039
2004	13.198
2005	13.74
2006	13.615
2007	16.229
2008	16.077
2009	15.061
2010	16.299
2011	17.239
2012	18.028
2013	17.57
2014	18.452
2015	19.473
2016	19.767
2017	19.999
2018	20.32
2019	20.646
2020	20.912
2021	21.173
2022	21.463