Year	Percent
1960	2.01598
1961	2.04468
1962	2.07106
1963	2.09417
1964	2.11375
1965	2.13216
1966	2.15123
1967	2.17413
1968	2.20313
1969	2.23966
1970	2.28229
1971	2.30483
1972	2.32596
1973	2.38712
1974	2.49807
1975	2.6281
1976	2.75016
1977	2.81897
1978	2.80487
1979	2.6922
1980	2.50706
1981	2.37481
1982	2.25065
1983	1.98248
1984	1.53716
1985	1.01111
1986	0.38418
1987	-0.10381
1988	-0.1407
1989	0.43788
1990	1.42956
1991	2.56591
1992	3.46532
1993	3.94199
1994	3.88639
1995	3.50039
1996	3.05641
1997	2.75055
1998	2.57374
1999	2.58118
2000	2.70863
2001	2.84319
2002	2.92055
2003	2.96983
2004	2.97857
2005	2.96058
2006	2.94057
2007	2.9311
2008	2.92402
2009	2.92146
2010	2.92129
2011	2.91963
2012	2.91473
2013	2.90848
2014	2.9007
2015	2.89142
2016	2.88121
2017	2.86988