Year	Percent
1980	4.383
1981	4.119
1982	4.132
1983	3.891
1984	3.926
1985	4.09
1986	4.249
1987	4.238
1988	4.066
1989	4.048
1990	3.727
1991	3.678
1992	3.285
1993	3.38
1994	3.474
1995	3.493
1996	3.372
1997	3.348
1998	3.273
1999	3.178
2000	3.165
2001	3.133
2002	3.137
2003	3.049
2004	3.064
2005	3.017
2006	2.977
2007	2.996
2008	3.059
2009	3.068
2010	3.134
2011	3.13
2012	3.093
2013	3.081
2014	2.993
2015	2.794
2016	2.616
2017	2.549
2018	2.49
2019	2.461
2020	2.437
2021	2.405
2022	2.374
2023	2.342
2024	2.311