Year	%
1987	26.2
1992	24.7
1995	23
2000	23.8
2003	25.6
2004	24.9
2005	25.2
2006	25.9
2007	26.2
2008	25.2
2009	26.7
2010	27.2
2011	27.3
2012	27.8
2013	28.5
2014	28.4
2015	28.2
2016	28.2
2017	28.7
2018	28.2
2019	27.7
2020	27.5
2021	28.3