Year	Percent
1991	14.182
1992	14.054
1993	15.557
1994	15.579
1995	15.613
1996	15.685
1997	16.346
1998	16.202
1999	16.216
2000	16.224
2001	16.383
2002	16.219
2003	16.3
2004	16.501
2005	16.618
2006	16.535
2007	16.546
2008	16.804
2009	16.583
2010	17.078
2011	17.311
2012	17.626
2013	17.035
2014	17.252
2015	17.445
2016	17.613
2017	17.694
2018	18.235
2019	18.412
2020	18.582
2021	18.778
2022	18.928