Year	Percent
1991	39.274
1992	39.724
1993	39.626
1994	39.817
1995	39.481
1996	39.314
1997	39.384
1998	38.65
1999	38.459
2000	38.114
2001	37.506
2002	36.92
2003	36.57
2004	35.831
2005	35.116
2006	35.551
2007	35.665
2008	34.803
2009	34.047
2010	33.451
2011	33.456
2012	34.546
2013	34.692
2014	33.229
2015	34.29
2016	34.05
2017	34.015
2018	33.777
2019	33.714
2020	33.584
2021	33.577
2022	33.486