Year	Percent
1991	31.56
1992	31.553
1993	31.487
1994	31.446
1995	31.372
1996	31.264
1997	31.197
1998	30.936
1999	30.746
2000	30.728
2001	30.622
2002	30.65
2003	30.513
2004	30.508
2005	30.469
2006	30.357
2007	30.043
2008	29.822
2009	29.728
2010	30.005
2011	29.871
2012	29.86
2013	29.852
2014	29.806
2015	29.812
2016	29.773
2017	29.721
2018	29.707
2019	29.693
2020	29.68
2021	29.668
2022	29.656