Year	Percent
1991	13.79
1992	13.568
1993	12.837
1994	12.131
1995	10.775
1996	10.454
1997	11.048
1998	11.742
1999	12.589
2000	12.247
2001	13.062
2002	12.796
2003	12.688
2004	13.424
2005	13.672
2006	12.437
2007	13.428
2008	12.788
2009	14.652
2010	15.638
2011	15.087
2012	17.434
2013	17.652
2014	17.442
2015	17.552
2016	17.597
2017	17.602
2018	17.661
2019	17.741
2020	17.85
2021	17.958
2022	18.053