Year	Percent
1991	79.738
1992	79.257
1993	78.758
1994	77.634
1995	76.809
1996	72.11
1997	72.115
1998	68.26
1999	68.286
2000	67.18
2001	60.988
2002	60.968
2003	57.276
2004	53.076
2005	51.533
2006	50.797
2007	48.906
2008	46.381
2009	44.045
2010	49.187
2011	47.914
2012	47.016
2013	48.136
2014	49.038
2015	50.969
2016	52.588
2017	53.519
2018	54.392
2019	54.819
2020	55.408
2021	55.48
2022	55.607