Year	Percent
1991	30.368
1992	30.451
1993	30.356
1994	30.33
1995	30.237
1996	30.261
1997	30.354
1998	30.396
1999	30.519
2000	30.647
2001	30.713
2002	30.866
2003	30.811
2004	30.858
2005	31.005
2006	31.004
2007	30.984
2008	30.966
2009	30.965
2010	30.98
2011	31.097
2012	31.016
2013	30.852
2014	30.678
2015	30.362
2016	30.176
2017	30.189
2018	30.215
2019	30.251
2020	30.294
2021	30.328
2022	30.367