Year	Percent
1980	2.176
1981	2.214
1982	2.137
1983	2.138
1984	2.169
1985	2.194
1986	2.164
1987	2.169
1988	2.167
1989	2.139
1990	2.058
1991	1.968
1992	1.784
1993	1.796
1994	1.823
1995	1.805
1996	1.768
1997	1.771
1998	1.792
1999	1.821
2000	1.828
2001	1.817
2002	1.818
2003	1.779
2004	1.742
2005	1.716
2006	1.672
2007	1.619
2008	1.589
2009	1.548
2010	1.516
2011	1.502
2012	1.482
2013	1.467
2014	1.458
2015	1.421
2016	1.391
2017	1.381
2018	1.359
2019	1.335
2020	1.314
2021	1.292
2022	1.268
2023	1.243
2024	1.219