Year	Percent
1991	17.759
1992	18.329
1993	19.001
1994	19.02
1995	18.052
1996	15.586
1997	16.196
1998	15.618
1999	15.447
2000	15.248
2001	14.391
2002	14.258
2003	14.727
2004	13.156
2005	13.444
2006	13.524
2007	13.95
2008	13.24
2009	12.963
2010	13.147
2011	12.973
2012	12.949
2013	13.008
2014	13.053
2015	13.097
2016	13.027
2017	13.221
2018	13.117
2019	13.062
2020	13.004
2021	12.936
2022	12.868