Year	Percent
1991	16.73
1992	17.07
1993	16.249
1994	16.855
1995	15.691
1996	16.125
1997	15.781
1998	15.095
1999	16.038
2000	15.549
2001	15.539
2002	14.208
2003	14.124
2004	14.897
2005	14.957
2006	15.652
2007	18.38
2008	18.309
2009	17.478
2010	16.925
2011	16.874
2012	16.609
2013	17.084
2014	16.778
2015	16.425
2016	16.516
2017	16.713
2018	16.882
2019	17.06
2020	17.273
2021	17.496
2022	17.722