Year	Percent
1991	14.415
1992	14.394
1993	14.541
1994	15.309
1995	15.603
1996	16.095
1997	16.294
1998	15.913
1999	16.089
2000	16.96
2001	16.827
2002	17.011
2003	17.096
2004	17.495
2005	18.001
2006	17.925
2007	17.872
2008	18.095
2009	17.372
2010	17.781
2011	18.366
2012	18.265
2013	18.287
2014	18.306
2015	17.853
2016	17.737
2017	17.8
2018	17.945
2019	18.051
2020	18.158
2021	18.265
2022	18.37