Year	Percent
1991	36.444
1992	36.537
1993	34.683
1994	35.104
1995	36.045
1996	37.112
1997	36.767
1998	36.414
1999	41.122
2000	36.312
2001	32.217
2002	32.346
2003	33.313
2004	35.034
2005	35.499
2006	37.149
2007	38.94
2008	40.015
2009	41.468
2010	39.575
2011	37.342
2012	34.474
2013	34.072
2014	32.849
2015	29.389
2016	29.357
2017	29.752
2018	30.037
2019	30.358
2020	30.792
2021	31.275
2022	31.82