Year	Percent
1991	15.362
1992	17.144
1993	19.891
1994	19.141
1995	19.029
1996	17.352
1997	16.147
1998	15.987
1999	16.469
2000	15.837
2001	17.411
2002	16.226
2003	15.102
2004	11.544
2005	9.455
2006	9.584
2007	10.116
2008	12.028
2009	9.823
2010	9.398
2011	9.759
2012	7.144
2013	7.988
2014	7.702
2015	7.365
2016	7.541
2017	7.574
2018	7.513
2019	7.415
2020	7.273
2021	7.203
2022	7.133