Cumulative black hole spin distribution predicted by the combined MCMC analysis based on X-ray and broad-line emission. Red and blue curves show the results for the high-mass and low-mass solutions, respectively. Assuming the high BH mass solution, the analysed population would systematically require low spin values, with a < 0.2 for ≈50% of sources, in order to remain consistent with the X-ray non-detections.