Year	Percent
1991	73.83912
1992	73.63327
1993	73.37203
1994	73.1743
1995	73.25155
1996	72.67849
1997	72.68386
1998	72.61416
1999	72.81407
2000	73.32263
2001	72.76437
2002	72.51373
2003	72.1217
2004	71.4346
2005	70.83019
2006	70.02107
2007	68.87472
2008	68.49831
2009	67.21381
2010	65.42469
2011	64.54607
2012	63.17393
2013	62.19298
2014	61.37177
2015	59.81431
2016	59.01297
2017	58.16997
2018	57.33429
2019	56.17168