Year	Percent
1991	39.583
1992	39.963
1993	40.217
1994	40.255
1995	39.934
1996	40.328
1997	40.546
1998	40.551
1999	40.378
2000	40.084
2001	40.205
2002	40.177
2003	40.034
2004	39.808
2005	39.531
2006	39.431
2007	39.214
2008	38.917
2009	38.567
2010	38.174
2011	37.911
2012	37.542
2013	37.095
2014	36.602
2015	36.094
2016	35.638
2017	35.465
2018	35.285
2019	35.105
2020	34.924
2021	34.745
2022	34.563