Year	Percent
1991	19.335
1992	17.795
1993	20.192
1994	21.611
1995	21.956
1996	18.985
1997	19.291
1998	21.117
1999	20.684
2000	21.23
2001	20.551
2002	19.608
2003	19.474
2004	21.73
2005	19.82
2006	21.341
2007	22.415
2008	21.625
2009	20.393
2010	18.39
2011	18.761
2012	19.317
2013	18.949
2014	21.628
2015	22.337
2016	21.873
2017	21.914
2018	22.112
2019	22.217
2020	22.346
2021	22.479
2022	22.611