Year	Percent
1991	56.444
1992	56.629
1993	56.498
1994	56.481
1995	55.918
1996	55.526
1997	55.021
1998	54.808
1999	54.504
2000	54.252
2001	53.892
2002	53.451
2003	53.271
2004	52.807
2005	52.421
2006	52.067
2007	51.627
2008	51.222
2009	48.098
2010	48.659
2011	51.186
2012	57.47
2013	52.321
2014	51.688
2015	52.572
2016	54.496
2017	54.408
2018	54.293
2019	54.174
2020	54.054
2021	53.934
2022	53.814