Year	Percent
1991	31.585
1992	31.819
1993	31.821
1994	31.527
1995	31.237
1996	30.807
1997	30.484
1998	30.9
1999	30.766
2000	30.479
2001	30.414
2002	30.288
2003	30.168
2004	29.538
2005	30.281
2006	30.022
2007	30.112
2008	28.977
2009	29.366
2010	29.404
2011	30.201
2012	29.969
2013	29.447
2014	30.088
2015	29.562
2016	29.3
2017	29.52
2018	30.069
2019	30.203
2020	30.229
2021	30.243
2022	30.225