Year	Percent
1991	27.65
1992	28.386
1993	26.808
1994	26.515
1995	27.865
1996	27.532
1997	25.416
1998	24.293
1999	20.477
2000	18.347
2001	21.629
2002	20.583
2003	20.445
2004	20.749
2005	20.637
2006	22.594
2007	23.476
2008	25.029
2009	23.442
2010	21.392
2011	18.848
2012	18.567
2013	18.145
2014	17.177
2015	16.643
2016	16.62
2017	17.019
2018	16.939
2019	16.539
2020	16.156
2021	15.855
2022	15.638