Year	Measure
1960	0.3332
1961	0.3444
1962	0.3308
1963	0.3447
1964	0.3309
1965	0.3643
1966	0.402
1967	0.4275
1968	0.4164
1969	0.3825
1970	0.4308
1971	0.3714
1972	0.3356
1973	0.3802
1974	0.3766
1975	0.4529
1976	0.3511
1977	0.4849
1978	0.4337
1979	0.4303
1980	0.4475
1981	0.4831
1982	0.4927
1983	0.4776
1984	0.4043
1985	0.4269
1986	0.4357
1987	0.4565
1988	0.4683
1989	0.3868
1990	0.3839
1991	0.4092
1992	0.4126
1993	0.4464
1994	0.4826
1995	0.4308
1996	0.35
1997	0.4128
1998	0.4046
1999	0.482
2000	0.4419
2001	0.4928
2002	0.4173
2003	0.4097
2004	0.3942
2005	0.3621
2006	0.3564
2007	0.403
2008	0.4091
2009	0.403
2010	0.4046
2011	0.3588