Year	Percent
1991	3.598
1992	3.517
1993	3.524
1994	3.54
1995	3.607
1996	3.55
1997	3.426
1998	3.503
1999	3.47
2000	3.428
2001	3.418
2002	3.423
2003	3.403
2004	3.389
2005	3.409
2006	3.42
2007	3.469
2008	3.63
2009	3.751
2010	3.769
2011	3.734
2012	3.592
2013	3.574
2014	3.476
2015	3.409
2016	3.399
2017	3.471
2018	3.414
2019	3.387
2020	3.372
2021	3.351
2022	3.332