Year	Percent
1991	21.09424
1992	20.9148
1993	20.74055
1994	20.49268
1995	20.4144
1996	20.07208
1997	19.74524
1998	19.32662
1999	18.37
2000	17.40546
2001	17.4603
2002	16.83754
2003	16.16629
2004	15.51152
2005	14.87911
2006	14.25347
2007	13.79239
2008	13.73554
2009	13.80526
2010	13.92138
2011	13.68805
2012	13.72252
2013	13.65262
2014	13.77153
2015	13.43128
2016	13.10362
2017	13.11789
2018	12.80951
2019	12.37326