Year	%
1990	16.4
1993	15.9
1996	15.9
1999	15.1
2002	14.4
2005	14.7
2008	14.5
2010	14.3
2011	14.6
2012	14.7
2013	15
2014	15.2
2015	15.3
2016	15.3
2017	15.1
2018	15.3
2019	15.2
2020	15.3