Year	Percent
1991	29.963
1992	30.577
1993	29.604
1994	29.172
1995	28.429
1996	27.314
1997	26.838
1998	26.017
1999	26.827
2000	24.396
2001	23.605
2002	23.573
2003	23.974
2004	24.551
2005	23.726
2006	22.558
2007	21.516
2008	20.609
2009	20.487
2010	19.275
2011	18.967
2012	15.464
2013	15.129
2014	14.076
2015	14
2016	14.107
2017	14.234
2018	14.029
2019	13.782
2020	13.558
2021	13.353
2022	13.159