[C II] luminosity as a function of halo mass obtained via abundance matching. The colours for the solid-line fits to the ALPINE data at z ≃ 5 are the same as in Fig. 1. The dashed red line refers to the LF fit obtained by Y20. The dotted gold and dark gold lines show the actual η₁ function (i.e. the mean total luminosity per halo) extracted by K25 at z = 5 and z = 4, respectively.