Year	Percent
1980	4.349
1981	4.322
1982	4.417
1983	4.36
1984	4.24
1985	4.16
1986	4.112
1987	4.061
1988	4.07
1989	4.097
1990	4.051
1991	3.998
1992	3.648
1993	3.556
1994	3.535
1995	3.481
1996	3.402
1997	3.344
1998	3.374
1999	3.372
2000	3.344
2001	3.33
2002	3.272
2003	3.17
2004	3.098
2005	3.005
2006	2.922
2007	2.84
2008	2.766
2009	2.697
2010	2.612
2011	2.564
2012	2.493
2013	2.426
2014	2.367
2015	2.316
2016	2.269
2017	2.235
2018	2.192
2019	2.15
2020	2.106
2021	2.063
2022	2.022
2023	1.982
2024	1.943