Year	Percent
1991	57.029
1992	57.033
1993	57.893
1994	58.751
1995	59.599
1996	60.43
1997	61.249
1998	62.059
1999	62.858
2000	63.645
2001	64.415
2002	65.163
2003	65.776
2004	66.322
2005	66.808
2006	67.214
2007	67.561
2008	67.859
2009	68.117
2010	68.402
2011	66.135
2012	66.202
2013	66.298
2014	66.396
2015	66.468
2016	66.611
2017	66.858
2018	67.106
2019	67.351
2020	67.589
2021	67.817
2022	68.043