Density profiles of red clump stars from APOGEE, Gaia RC-GSP-Spec, and their combined data sets (from top to bottom). The left panels show the radial density profiles Σ(R) obtained in six ranges of metallicity in the α-poor disc ([α/Fe]< 0.1 dex). The profiles are shifted by an arbitrary offset to be visually separated. The panels on the right represent the flaring scale length and vertical scale height predicted by our model for each metallicity bin. The shaded areas (left) and error bars (right) represent the 95% confidence interval. The Gaia RC-GSP-Spec star sample covers a smaller range in R, especially at low metallicity. We list the best-fit parameters in Table D.1.