  We report on recent progress by the HotQCD collaboration in studying the
trace anomaly at non-zero temperature in 2+1 flavor QCD on lattices with the
temporal extent N_tau=4, 6, 8, 10 and 12 using the highly improved staggered
quark (HISQ) action as well as the asqtad action. We discuss the dependence of
our lattice results on the scale setting procedure and compare them with hadron
resonance gas (HRG) calculations as well as to resummed perturbative results.
