Year	Percent
1991	9.668
1992	9.573
1993	9.613
1994	9.542
1995	9.827
1996	9.991
1997	10.03
1998	9.877
1999	9.692
2000	9.867
2001	10.125
2002	10.754
2003	11.16
2004	11.756
2005	12.196
2006	12.625
2007	13.065
2008	14.098
2009	14.873
2010	15.737
2011	16.218
2012	16.658
2013	16.989
2014	17.569
2015	18.327
2016	17.927
2017	18.288
2018	18.717
2019	19.118
2020	19.509
2021	19.781
2022	19.964