Year	Percent
1991	66.277
1992	66.281
1993	66.149
1994	65.847
1995	65.35
1996	64.727
1997	63.948
1998	63.008
1999	61.9
2000	60.631
2001	59.068
2002	57.352
2003	55.481
2004	53.513
2005	51.519
2006	49.849
2007	48.235
2008	46.636
2009	45.029
2010	43.434
2011	42.131
2012	40.787
2013	39.464
2014	38.231
2015	37.118
2016	36.02
2017	35.899
2018	35.775
2019	35.63
2020	35.454
2021	35.259
2022	35.034