Year	Percent
1991	17.365
1992	17.711
1993	17.56
1994	17.86
1995	18.05
1996	18.289
1997	18.373
1998	18.513
1999	18.698
2000	18.631
2001	18.496
2002	18.42
2003	18.235
2004	18.09
2005	17.988
2006	17.292
2007	16.528
2008	16.042
2009	15.579
2010	14.968
2011	14.651
2012	14.379
2013	14.091
2014	13.846
2015	13.593
2016	13.715
2017	13.508
2018	13.307
2019	13.114
2020	12.912
2021	12.7
2022	12.475