Year	Percent
1991	14.449
1992	15.156
1993	15.423
1994	15.63
1995	16.17
1996	16.069
1997	16.551
1998	16.913
1999	17.279
2000	17.627
2001	18.16
2002	18.483
2003	18.613
2004	19.464
2005	19.841
2006	20.546
2007	20.999
2008	21.466
2009	21.887
2010	22.007
2011	21.021
2012	20.449
2013	19.605
2014	18.857
2015	18.834
2016	18.928
2017	18.805
2018	19.337
2019	19.672
2020	19.642
2021	19.631
2022	19.606