Lepton charge asymmetry for muons from W$^\pm$-boson decays with $\pt^\mu > 10$ GeV/$c$ in p-Pb collisions at $\sqrt{s_{\rm NN}}=8.16$ TeV. The measurements are compared with predictions from pQCD calculations with several nPDF sets as well as with calculations based on the CT14 PDF without nuclear modifications. All the calculations include the isospin effect. The bottom panels show the ratio of the calculated to the measured asymmetry. The horizontal bars correspond to the width of the rapidity intervals. The vertical bars and boxes indicate the statistical and systematic uncertainties, respectively. The data points are placed at the centres of the rapidity intervals while the theory points are horizontally shifted for better visibility.