Year	Percent
1991	19.67
1992	20.095
1993	20.207
1994	19.278
1995	18.603
1996	19.825
1997	20.334
1998	19.007
1999	21.722
2000	21.879
2001	22.173
2002	21.728
2003	22.763
2004	23.685
2005	23.579
2006	23.79
2007	23.528
2008	23.201
2009	23.198
2010	23.1
2011	22.921
2012	22.327
2013	22.606
2014	22.474
2015	22.429
2016	22.542
2017	22.454
2018	22.397
2019	22.295
2020	22.203
2021	22.111
2022	22.019