Year	Percent
1991	70.10572
1992	69.10533
1993	68.93625
1994	68.72255
1995	66.68853
1996	65.17629
1997	63.38612
1998	62.79574
1999	62.38242
2000	61.12467
2001	60.5071
2002	59.35486
2003	57.83599
2004	56.85358
2005	56.10766
2006	55.13287
2007	54.704
2008	53.88896
2009	53.29104
2010	53.13658
2011	52.79667
2012	52.60052
2013	52.39927
2014	52.19698
2015	51.68996
2016	51.20072
2017	50.61529
2018	48.12338
2019	48.8803