Year	Percent
1991	17.242
1992	16.989
1993	18.425
1994	17.079
1995	18.066
1996	19.107
1997	22.112
1998	23.252
1999	19.235
2000	22.771
2001	20.676
2002	20.435
2003	20.234
2004	19.985
2005	19.984
2006	18.109
2007	17.189
2008	16.256
2009	19.339
2010	19.623
2011	19.716
2012	19.137
2013	19.253
2014	12.97
2015	13.139
2016	13.278
2017	13.162
2018	12.734
2019	12.291
2020	11.925
2021	11.573
2022	11.232