Year	Percent
1991	23.43154
1992	23.26993
1993	23.05815
1994	22.87681
1995	22.58622
1996	22.32476
1997	22.0269
1998	21.74225
1999	21.3983
2000	20.9948
2001	20.57414
2002	20.01555
2003	19.46896
2004	18.90364
2005	18.27063
2006	17.65675
2007	17.10239
2008	16.68665
2009	16.2405
2010	15.75985
2011	15.31786
2012	14.78902
2013	14.33362
2014	13.95541
2015	13.54944
2016	13.20458
2017	12.85557
2018	12.49921
2019	12.14769