et al. 2004, Garn et al. 2009b), although such conclusions are sensitive to the assumed infrared SEDs and associated “k-corrections”. Indeed, using recent [*BLAST*]{} stacking measurements, Ivison et al. (2009) reported evidence for a tentative decline in $q_{\rm{IR}}$ (defined as the logarithmic ratio of the the bolometric 8–1000 infrared to monochromatic 1.4 GHz radio fluxes), of the form $q_{\rm{IR}} \propto (1+z)^{-0.15 \pm 0.03}$ (see also Kovacs et al. 2006).

The far-infrared luminosity, L(FIR), is traditionally defined through a linear combination of IRAS 60 and 100 flux densities (see Sanders & Mirabel 1996), which for an SED consisting of a superposition of modified blackbodies yields the 42.5–122.5 luminosity to sub-percent accuracy (Helou et al. 1988). Given L(FIR), galaxies were assigned a model SED from the library of star-forming galaxy templates assembled by Rieke et al. (2009). The latter consists of 14 SEDs uniformly spaced in total infrared luminosity (8–1000), L(TIR), from log L(TIR)() = 9.75 to 13.00. The templates were taken from the online version of Table 4 in Rieke et al. (2009) but they terminate on the short wavelength side at 5.26 for those with log L(TIR) () $\leq 11$ and at 4.02 at higher luminosities. In order to predict 