Year	Percent
1991	15.19
1992	15.357
1993	15.483
1994	16.076
1995	15.729
1996	15.261
1997	14.762
1998	14.954
1999	15.149
2000	15.452
2001	15.764
2002	14.18
2003	14.638
2004	15.297
2005	15.879
2006	17.231
2007	19.548
2008	20.758
2009	20.779
2010	22.885
2011	24.532
2012	26.342
2013	22.886
2014	20.254
2015	18.162
2016	18.435
2017	18.323
2018	18.548
2019	18.857
2020	19.182
2021	19.497
2022	19.816