Year	Percent
1971	50.10504
1972	61.59069
1973	67.42081
1974	66.52506
1975	73.02474
1976	73.80597
1977	72.51218
1978	90.04584
1979	91.3259
1980	89.74209
1981	84.37673
1982	89.09276
1984	85.82569
1985	87.52755
1986	86.70257
1987	74.7646
1988	78.82353
1989	77.54905
1990	75.23981
1991	73.02028
1992	68.77593
1993	65.95797
1994	65.21532
1995	63.41916
1996	54.14454
1998	93.42409
1999	95.11973
2003	94.24084
2005	93.97089
2006	94.0914
2007	100.56139
2008	102.37542
2009	104.97001
2011	101.90765
2013	99.73921
2014	96.17699
2015	93.68974
2016	94.21644