Year	Percent
1991	13.789
1992	13.286
1993	13.144
1994	13.465
1995	13.498
1996	13.053
1997	12.967
1998	12.493
1999	12.67
2000	12.324
2001	12.256
2002	12.364
2003	12.87
2004	13.154
2005	13.058
2006	13.292
2007	13.454
2008	13.416
2009	13.671
2010	14.071
2011	14.255
2012	14.732
2013	14.704
2014	15.325
2015	15.063
2016	15.498
2017	15.421
2018	15.376
2019	15.327
2020	15.252
2021	15.167
2022	15.083