Year	Percent
1991	3.105
1992	2.964
1993	2.974
1994	2.618
1995	2.612
1996	2.636
1997	2.559
1998	2.568
1999	2.576
2000	2.573
2001	2.587
2002	2.613
2003	2.639
2004	2.656
2005	2.674
2006	2.671
2007	2.7
2008	2.708
2009	2.712
2010	2.734
2011	2.751
2012	2.771
2013	2.786
2014	2.799
2015	2.808
2016	2.82
2017	2.822
2018	2.845
2019	2.876
2020	2.908
2021	2.944
2022	2.971