Year	Percent
1991	13.631
1992	14.008
1993	14.058
1994	13.814
1995	13.506
1996	14.351
1997	14.614
1998	14.903
1999	14.935
2000	15.816
2001	15.521
2002	15.986
2003	16.314
2004	16.943
2005	17.132
2006	17.419
2007	18.088
2008	18.232
2009	18.01
2010	19.15
2011	17.617
2012	15.143
2013	15.114
2014	15.052
2015	15.137
2016	15.34
2017	15.175
2018	15.213
2019	15.273
2020	15.333
2021	15.4
2022	15.473