Distributions of submillimetre sources as a function of declination. The blue histogram is for starless cores, the red histogram for protostellar cores, the grey one for sources with undetermined stage of evolution, and the black histogram for all sources. In the lower panel, the black circles show the ratio between the numbers of protostellar and starless cores in each bin, and the orange diamonds show the ratio for individual sources. The vertical dashed lines show the limits of the area that is mapped with the IRAM 30 m telescope.