Year	Percent
1991	29.582
1992	29.577
1993	29.584
1994	29.594
1995	29.652
1996	29.841
1997	30.064
1998	30.297
1999	30.581
2000	30.876
2001	27.939
2002	27.953
2003	28.197
2004	29.095
2005	28.75
2006	28.993
2007	29.584
2008	29.88
2009	30.365
2010	30.793
2011	31.282
2012	31.765
2013	31.983
2014	32.186
2015	32.344
2016	32.48
2017	32.416
2018	32.334
2019	32.258
2020	32.194
2021	32.17
2022	32.161