Observed L_IR/L_UV ratio as a function of the UV slope β (at 2000 Å rest-frame) for our objects (black symbols), and for the local starbursts of Meurer et al. (1999; M99), revised by Takeuchi et al. (2012) in green (the corrected IRX-β curve is shown with the solid red line, and the M99 relation is shown for reference in the gray dashed line). All our values for β are the mean from the Calzetti- and the SMC-based models. For the Cosmic Eye and cB58 we plot the spectroscopically measured slopes available in the literature. The expected relation for constant SFR and age ≳100 Myr for the SMC (blue dashed-dotted) attenuation/extinction law is also plotted. High-z ULIRGs (e.g. Oteo et al. 2013) tend to populate the region above the M99 relation. Discussion in the text.