Year	Percent
1991	37.429
1992	37.59
1993	37.168
1994	41.166
1995	39.877
1996	39.663
1997	39.286
1998	37.607
1999	35.267
2000	39.328
2001	39.287
2002	40.533
2003	37.399
2004	34.847
2005	38.772
2006	35.247
2007	36.421
2008	35.403
2009	38.494
2010	36.61
2011	36.951
2012	37.104
2013	36.751
2014	35.067
2015	35.512
2016	34.543
2017	34.544
2018	34.36
2019	34.216
2020	34.065
2021	33.923
2022	33.784