Box plot showing the Q distribution versus the ratio of gas to stellar mass, coloured according to the luminosity of the regions within which they reside. The boxes extend from the first to the third quartiles, with a red line at the median Q value. The whiskers extend from the box by ±1.5 times the box size. Disks with Q ≲ 2 are Toomre unstable (i.e. all but Cep A & NGC 753 8IRS9).