Year	Percent
1991	83.336
1992	82.58
1993	82.997
1994	86.012
1995	84.429
1996	84.027
1997	83.657
1998	83.621
1999	83.286
2000	83.088
2001	82.796
2002	81.968
2003	81.307
2004	80.326
2005	79.05
2006	77.566
2007	75.963
2008	73.964
2009	72.684
2010	70.825
2011	68.978
2012	66.896
2013	62.952
2014	57.936
2015	56.63
2016	56.185
2017	55.643
2018	54.757
2019	53.747
2020	52.721
2021	51.655
2022	50.571