Relative bias for the inferred value of Φ(400 pc)−Φ(0 pc) using Jeans analysis under the assumption of equilibrium and in the presence of a phase-space spiral as a function of θ₀. The top panels show the relative perturbation of the spiral (unlike Fig. A.2, which showed the total number densities), where red (blue) correspond to a over-density (under-density), whose relative amplitude is in the range [ − 20, 20]%.