Year	Percent
1991	3.43238
1992	3.40511
1993	3.37948
1994	3.32638
1995	3.28164
1996	3.22493
1997	3.16519
1998	3.11879
1999	3.05245
2000	2.96216
2001	2.88731
2002	2.81152
2003	2.74636
2004	2.65552
2005	2.56283
2006	2.46784
2007	2.38389
2008	2.33435
2009	2.32447
2010	2.27122
2011	2.28907
2012	2.28865
2013	2.28004
2014	2.23879
2015	2.19265
2016	2.1399
2017	2.09541
2018	2.04204
2019	1.99412