Population prior on kinematic misalignment angle Δφ_kin ≡ |φ_kin−φ_light| for a sample of slow rotator elliptical galaxies from the SDSS’s MaNGA dataset (Li et al. 2018). Here, Δφ_kin = 0° corresponds to a purely oblate shape, and Δφ_kin = 90° corresponds to a purely prolate shape. The vertical dashed gray lines mark Δφ_kin = 0°, 45°, and 90°. The red points with error bars show the measurements from Li et al. (2018). We fit this distribution with a double Gaussian model (blue line) with the means fixed to Δφ_kin = 0° and Δφ_kin = 90°. We take Δφ_kin < 45° as the oblate case and Δφ_kin > 45° as the prolate case. Integrating the double Gaussian model from 0° to 45° gives the prior probability of oblateness p(oblate)_pop ≃ 0.65.