Year	%
1987	22.2
1991	22.9
1995	23.5
2000	27.2
2003	27.7
2004	27.9
2005	27.6
2006	28
2007	28.3
2008	27.8
2009	27.5
2010	27.7
2011	27.6
2012	27.1
2013	27.2
2014	26.8
2015	27.1
2016	27.1
2017	27.4
2018	27.3
2019	27.7
2020	27.1
2021	27.7