Year	Percent
1991	18.076
1992	18.587
1993	18.965
1994	19.297
1995	15.888
1996	16.623
1997	15.521
1998	14.638
1999	13.81
2000	13.577
2001	13.029
2002	12.907
2003	12.803
2004	12.509
2005	12.693
2006	12.919
2007	12.624
2008	12.849
2009	13.65
2010	13.432
2011	13.404
2012	13.617
2013	13.477
2014	14.035
2015	14.26
2016	14.065
2017	14.105
2018	14.013
2019	13.935
2020	13.878
2021	13.823
2022	13.773