Effective survey area as a function of redshift and M₁₄₅₀. The contours are plotted at 10 deg², 40 deg², 70 deg², 100 deg², and 130 deg². The effective survey area includes the efficiency of the color selection for the mock quasars. The upper and lower edges are determined with i > 20.0 and i < 24.0 mag selection criteria. The gap seen in the middle reflects the effect of the masks around HSC objects brighter than i < 22.0 mag. For objects brighter than i < 22.0 mag, the masks are not applied. The completeness of the stellar classification is not included in the calculation.