Fed officials in December thought labor-market slack had "diminished appreciably" since earlier in 2015, with improvements in the unemployment rate and key measures of underemployment. A number of officials also noted a pickup in wage increases, according to the meeting minutes. But some officials cautioned further progress would be necessary before reaching the central bank's goal of maximum employment. And labor-force participation keeps falling, though some officials attributed that to demographic factors while others saw a rise in structural detachment among prime-age men.