Year	Percent
1991	67.611
1992	69.255
1993	68.519
1994	68.202
1995	69.167
1996	68.309
1997	68.784
1998	69.832
1999	65.956
2000	66.499
2001	67.869
2002	68.408
2003	69.381
2004	70.399
2005	70.7
2006	71.56
2007	72.867
2008	74.163
2009	75.682
2010	76.614
2011	77.086
2012	77.386
2013	77.599
2014	78.207
2015	78.71
2016	78.869
2017	78.899
2018	79.115
2019	79.278
2020	79.49
2021	79.674
2022	79.835