Percentage of complex sources for each longitude bin of 4 deg (black circles). The x error bars indicate the extent of the bin, and the y errors are determined through bootstrapping. The dashed line shows the percentage of complex sources for the full sample at 42%. The cyan-shaded regions indicate longitudes which correspond to the Galactic spiral arms listed in the text and the longitude range within 5 degrees of the Galactic centre. The bottom panel is a histogram showing the number of sources in each longitude bin. The green triangle shows the percentage of complex sources at 355° < l < 360° in Livingston et al. (2021).