Differential 70 (left) and 160 μm (right) background brightness dν_νB_ν / dz as a function of redshift, in units of nW m^-2 sr^-1, as predicted by 4 models: dash black line: Lagache et al. (2004) model; Dot magenta line: Le Borgne et al. (2009) model; Dot-dash grey line: Valiante et al. (2009); Dot-dot-dot-dash blue line: Bethermin et al. (2010c) model. For each model, the top line corresponds to all galaxies, and the bottom line to the prior selection (used in this work) of S₂₄ > 80   μ Jy.