Year	Percent
1971	55.29558
1972	52.138
1973	55.49584
1974	57.45904
1975	60.11529
1976	61.1502
1977	61.29146
1978	53.53508
1979	35.67522
1980	45.78979
1981	54.54522
1986	72.71884
1987	73.29875
1997	85.78471
1999	89.14234
2000	87.5462
2001	86.25207
2002	85.54579
2003	86.44051
2004	88.60257
2005	90.31769
2006	86.8409
2007	91.93711
2009	97.16879
2010	100.54553
2013	100.49398
2016	93.9447