Year	Percent
1991	70.20516
1992	70.21539
1993	70.06813
1994	70.41561
1995	70.29329
1996	70.04727
1997	69.89731
1998	69.96909
1999	70.41684
2000	70.87917
2001	71.22861
2002	71.57409
2003	71.779
2004	71.97574
2005	72.26154
2006	72.01428
2007	71.73114
2008	71.43287
2009	68.09153
2010	64.33325
2011	60.42591
2012	56.03032
2013	54.47283
2014	53.27894
2015	52.26535
2016	51.37091
2017	50.71013
2018	50.10653
2019	49.64715