Year	%
1984	27
1987	26.1
1990	27
1993	27.8
1996	29.7
1998	26.8
1999	27.3
2000	25
2001	25.6
2002	27.7
2003	27.2
2004	27.7
2005	28
2006	28.8
2007	29.6
2008	29.1
2009	29.4
2010	29.5
2011	32.6
2012	32.9
2013	32.9
2014	32.5
2015	33
2016	31
2017	30.2
2018	29.9
2019	29.5
2020	29.5
2021	30.1
2022	30.7
2023	31.4