Year	Percent
1991	28.694
1992	26.698
1993	21.346
1994	18.605
1995	18.517
1996	19.825
1997	25.531
1998	29.022
1999	20.912
2000	23.543
2001	25.019
2002	25.642
2003	26.017
2004	29.314
2005	30.898
2006	30.837
2007	30.951
2008	30.297
2009	18.499
2010	18.927
2011	19.287
2012	18.786
2013	19.144
2014	15.888
2015	15.95
2016	17.253
2017	17.215
2018	17.384
2019	17.437
2020	17.469
2021	17.515
2022	17.516