Year	Percent
1971	40.53529
1972	44.25836
1973	49.81328
1974	51.25183
1975	51.0677
1976	50.35754
1977	51.66468
1981	46.45834
1982	49.40349
1983	50.64081
1984	48.73848
1987	61.85829
1988	65.50327
1989	63.30771
1991	66.47685
1992	67.97595
1993	70.81069
1995	72.94251
1996	78.10901
1998	81.78877
2000	91.39715
2001	90.14744
2002	88.83112
2003	88.18828
2005	89.43695
2006	89.3089
2007	93.63223
2008	95.11255
2009	97.85452
2010	100.13377
2011	103.77667
2012	103.87051
2013	102.30797
2014	100.57818
2015	96.72319
2016	93.40382