Year	Percent
1971	37.01799
1972	35.20997
1973	43.39842
1974	40.95408
1999	71.93445
2000	78.24854
2001	77.60894
2002	78.67719
2003	80.98034
2004	82.9887
2006	87.46022
2007	87.54249
2008	88.27555
2009	86.77792
2010	86.46871
2014	86.58381
2017	88.85305