  Researchers at the National Institute of Standards and Technology(NIST) have
measured the value of the Planck constant to be $h =6.626\,069\,934(89)\times
10^{-34}\,$J$\,$s (relative standard uncertainty $13\times 10^{-9}$). The
result is based on over 10$\,$000 weighings of masses with nominal values
ranging from 0.5$\,$kg to 2$\,$kg with the Kibble balance NIST-4. The
uncertainty has been reduced by more than twofold relative to a previous
determination because of three factors: (1) a much larger data set than
previously available, allowing a more realistic, and smaller, Type A
evaluation; (2) a more comprehensive measurement of the back action of the
weighing current on the magnet by weighing masses up to 2$\,$kg, decreasing the
uncertainty associated with magnet non-linearity; (3) a rigorous investigation
of the dependence of the geometric factor on the coil velocity reducing the
uncertainty assigned to time-dependent leakage of current in the coil.
