Year	%
1997	16.02
1998	15.38
1999	15.44
2000	16.21
2001	15.09
2002	11.32
2003	10.59
2004	10.09
2005	12.02
2006	13.11
2007	14.4
2008	15.68
2009	16.77
2010	18.12
2011	18.55
2012	19.72
2013	20.24
2015	20.96
2016	21.64
2017	21.71
2018	20.16
2019	19.65
2020	18.18
2021	18.09