Dust-to-stellar mass ratio as a function of redshift for our SMGs and the flux-limited ALESS SMGs. The green filled circles represent the mean values of the binned AzTEC data (each bin contains four SMGs), while the cyan filled circles represent the mean values of the binned ALESS data (each bin contains five SMGs). The error bars of the binned data points represent the standard errors of the mean values. The horizontal dashed lines indicate the corresponding median values of and , respectively.