Upper panel: quarterly median transit depth residuals, as derived from the Kepler PDC-MAP light curve of Kepler-423, against Kepler crowding metrics. Error bars are the median absolute deviations. Quarters sharing the same Kepler observing season are plotted with the same symbol and colour: Q₁, Q₅, Q₉, Q₁₃, and Q₁₇ (upward green triangles); Q₂, Q₆, Q₁₀, and Q₁₄ (downward black triangles); Q₃, Q₇, Q₁₁, and Q₁₅ (blue squares); Q₄, Q₈, Q₁₂, and Q₁₆ (red circles). Lower panel: same as before, but for the PDC-MAP cotrended data, following our quarterly crowding metric correction constrained by an informative prior. The x-axis reports our estimates of the quarterly crowding metrics (Table 4).