Year	Percent
1991	68.878
1992	66.559
1993	64.723
1994	65.721
1995	67.189
1996	65.821
1997	67.849
1998	68.857
1999	69.931
2000	71.086
2001	66.596
2002	62.884
2003	58.202
2004	52.514
2005	48.01
2006	42.526
2007	36.452
2008	31.248
2009	26.255
2010	20.084
2011	18.953
2012	18.149
2013	17.697
2014	17.271
2015	15.476
2016	15.436
2017	15.383
2018	15.239
2019	14.908
2020	14.61
2021	14.323
2022	14.008