LAE volume densities as a function of redshift and limiting Lyα luminosity. The datapoints are collected from 18 publications, searching for LAEs, with colour coding referring to the limiting Lyα luminosity in each survey (where [blue, yellow, red] have log       Lyα [<42.25, 42.25 − 42.75,  > 42.75] erg s^-1). Models (see text) come from Bongiorno et al. (2007, B07) and Hopkins et al. (2007, H07). To the left, all measurements and the two models (with M_B <  −22.0) are shown to the different Lyα luminosity limits. To the right, only models and measurements to the faintest luminosity limits are shown, and instead the effect of varying the luminosity of the AGN is shown. For each model the grey lines show the predictions for M_B <  −20.0 (above the original line) or M_B <  −24.0 (below the original line).