Year	Percent
1991	20.771
1992	21.994
1993	21.27
1994	16.605
1995	19.8
1996	15.426
1997	19.856
1998	18.158
1999	18.897
2000	16.066
2001	19.176
2002	19.055
2003	18.997
2004	18.424
2005	18.357
2006	20.798
2007	22.697
2008	23.133
2009	22.405
2010	21.651
2011	22.783
2012	20.596
2013	20.325
2014	22.218
2015	20.576
2016	20.548
2017	23.201
2018	22.828
2019	22.421
2020	22.003
2021	21.628
2022	21.245