Illustration of the method used to determine the SFRD_IR. Left panel: steps performed. Right panel: arbitrary proxy density function (UVLF or GSMF) and a power law relation between the property used as a proxy and the FIR flux. The black squares represent measured values and the solid line the fit with uncertainties represented by a shaded region. The vertical shaded regions show the proxy range, in which the data is available for both the power law relation derived from ALPINE and the proxy density function.