Year	Percent
1991	17.686
1992	16.508
1993	16.583
1994	16.798
1995	16.62
1996	16.41
1997	16.259
1998	15.942
1999	15.524
2000	15.406
2001	15.036
2002	14.807
2003	15.007
2004	15.158
2005	14.932
2006	14.964
2007	15.033
2008	15.046
2009	15.209
2010	15.029
2011	15.101
2012	15.51
2013	15.883
2014	16.308
2015	16.459
2016	16.676
2017	16.866
2018	17.187
2019	17.614
2020	17.956
2021	18.32
2022	18.723