Year	Percent
1991	31.681
1992	31.739
1993	31.593
1994	31.835
1995	32.136
1996	32.223
1997	32.406
1998	32.351
1999	32.427
2000	32.013
2001	31.763
2002	30.423
2003	30.37
2004	30.364
2005	30.375
2006	30.355
2007	30.247
2008	30.257
2009	30.214
2010	30.14
2011	30.321
2012	30.689
2013	30.828
2014	30.673
2015	30.613
2016	30.57
2017	30.521
2018	30.447
2019	30.376
2020	30.307
2021	30.246
2022	30.187