Flux density number distribution for ATLASGAL sources extracted by SExtractor (grey filled histogram) and the BGPS (blue histogram). In both plots the peak of the BGPS distribution has been normalised to the peak of the ATLASGAL distribution. In the left and right panels we present histograms of the peak and integrated flux densities measured for each source respectively. The red line on each plot shows the result of a linear least-squares fit to flux densities larger than the peak of each distribution.