Year	Percent
1991	17.354
1992	16.811
1993	16.797
1994	17.789
1995	17.507
1996	17.105
1997	16.538
1998	17.198
1999	17.015
2000	17.024
2001	17.404
2002	17.515
2003	18.28
2004	18.736
2005	18.826
2006	18.967
2007	19.556
2008	19.642
2009	18.393
2010	19.358
2011	19.257
2012	18.825
2013	19.212
2014	18.788
2015	18.759
2016	18.568
2017	18.914
2018	19.033
2019	18.235
2020	18.292
2021	18.346
2022	18.421