Left-hand panels: total number of sources present in the J, H, and K_s singleband and in the JHK_s multi-band catalogue for each VVV bulge tile. The tiles are numbered from b201 to b396, starting at the bottom-left corner of the VVV bulge area (l,b = −10, − 10). The Galactic latitude for the tile centres is shown in the figure, while dashed lines mark the edge of each line of tiles across the bulge. The right-hand panel presents a histogram with the ratio between the number of sources in the multi-band catalogue in relation to its least numerous single-band catalogue.