Year	Percent
1991	18.137
1992	18.377
1993	18.194
1994	16.597
1995	15.258
1996	16.615
1997	16.857
1998	14.614
1999	18.295
2000	18.03
2001	17.865
2002	17.616
2003	17.599
2004	17.704
2005	17.52
2006	17.33
2007	17.158
2008	16.396
2009	16.278
2010	16.089
2011	15.6
2012	14.278
2013	14.38
2014	14.392
2015	13.804
2016	14.285
2017	14.112
2018	13.905
2019	13.634
2020	13.419
2021	13.234
2022	13.075