Year	Percent
1991	40.606
1992	39.455
1993	39.383
1994	39.334
1995	39.079
1996	38.899
1997	39.137
1998	37.331
1999	37.592
2000	39.385
2001	38.09
2002	35.549
2003	35.278
2004	37.896
2005	35.94
2006	35.901
2007	35.529
2008	35.356
2009	34.991
2010	34.68
2011	34.423
2012	32.348
2013	32.082
2014	31.776
2015	31.555
2016	31.354
2017	31.315
2018	31.302
2019	31.287
2020	31.271
2021	31.253
2022	31.235