Year	%
1987	33
1991	33.6
1995	34.4
2000	36.9
2003	37.2
2004	37.4
2005	37.2
2006	37.4
2007	37.6
2008	37.2
2009	36.9
2010	37
2011	37.1
2012	36.7
2013	36.6
2014	36.4
2015	36.7
2016	36.6
2017	36.9
2018	36.8
2019	37.1
2020	36.7
2021	37.1