Year	Percent
1991	70.88323
1992	69.80671
1993	68.77627
1994	67.8237
1995	66.96568
1996	66.30373
1997	65.27902
1998	64.76546
1999	64.98598
2000	65.25243
2001	63.98913
2002	62.03914
2003	59.67461
2004	57.89467
2005	54.82782
2006	51.66451
2007	49.28318
2008	48.61893
2009	47.5526
2010	48.70731
2011	48.30113
2012	47.359
2013	46.809
2014	46.33304
2015	44.01829
2016	41.86487
2017	40.15535
2018	38.7024
2019	37.21892