Euclidean-normalized differential number counts of extragalactic sources at 24 μm compared with our model fit. The red circles are from the analysis of SWIRE survey data by Shupe et al. (2008), black squares from Papovich et al. (2004). The contribution by type-I AGNs is shown as green dot-dashed line, moderate-luminosity starbursts (the LIRGs) make the cyan short-dash line (type-II AGNs and starbursts are included in the same population on the assumption that in both classes the IR spectrum is dominated by starburst emission). The red long-dashed line corresponds to the population of high-luminosity sources dominating the IR emissivity at high redshifts. The dotted line is the separate contribution of normal spirals, while the continuous line is the total model counts.