Year	Percent
1991	19.592
1992	23.886
1993	23.009
1994	23.662
1995	21.957
1996	21.207
1997	19.045
1998	17.324
1999	17.184
2000	15.305
2001	15.318
2002	15.189
2003	17.61
2004	18.157
2005	18.902
2006	14.948
2007	13.566
2008	13.996
2009	14.173
2010	15.492
2011	15.382
2012	12.173
2013	9.89
2014	7.983
2015	7.428
2016	5.548
2017	5.488
2018	5.278
2019	5.082
2020	4.87
2021	4.664
2022	4.478