Year	Percent
1991	23.459
1992	22.67
1993	21.358
1994	21.013
1995	20.996
1996	20.449
1997	19.834
1998	22.463
1999	22.554
2000	22.601
2001	21.464
2002	21.847
2003	20.655
2004	22.332
2005	20.144
2006	19.568
2007	19.798
2008	19.674
2009	18.939
2010	16.236
2011	13.019
2012	10.131
2013	9.514
2014	10.848
2015	11.307
2016	11.54
2017	12.006
2018	12.147
2019	12.942
2020	13.128
2021	13.19
2022	13.086