Maximal polarization levels, P_max, as a function of the power-law index of the energy angular profile, a, for various viewing angles and random magnetic field in the plane of the shock (ξ → 0). Values of a ≤ 2 and a > 2 correspond to shallow and steep jets, respectively. While jets observed from within their core opening angle θ_c (q < 1, solid lines) exhibit a power-law trend, P_max ∝ a^1.3, jets observed off-axis (q > 1, dotted lines) show a broken power-law behavior, which rises as ∝a^1.4 before asymptotically approaching a constant level of polarization. The value of a_crit where the turnover occurs depends on q due to the impact of the jet structure on its effective core size θ_c,eff.