Year	Percent
1980	7.883
1981	8.077
1982	8.319
1983	8.397
1984	8.406
1985	8.542
1986	8.525
1987	8.596
1988	8.785
1989	8.886
1990	8.954
1991	9.045
1992	8.192
1993	7.993
1994	7.84
1995	7.77
1996	7.72
1997	7.493
1998	7.216
1999	6.957
2000	6.822
2001	6.689
2002	6.507
2003	6.348
2004	6.165
2005	5.981
2006	5.758
2007	5.552
2008	5.336
2009	5.067
2010	5.015
2011	4.812
2012	4.734
2013	4.671
2014	4.531
2015	4.438
2016	4.324
2017	4.25
2018	4.139
2019	4.048
2020	3.926
2021	3.811
2022	3.699
2023	3.589
2024	3.483