Year	Percent
1991	21.533
1992	21.654
1993	21.915
1994	21.534
1995	21.214
1996	21.144
1997	20.943
1998	20.593
1999	20.108
2000	19.67
2001	19.952
2002	19.623
2003	19.431
2004	19.154
2005	18.976
2006	18.917
2007	19.014
2008	18.417
2009	17.559
2010	16.301
2011	15.282
2012	14.379
2013	14.289
2014	14.172
2015	13.958
2016	14.029
2017	14.112
2018	14.189
2019	14.318
2020	14.444
2021	14.542
2022	14.637