Contribution of different redshift shells in Eq. (15) to the WD component of the AGWB for 25 frequency bins in the range [10⁻⁵, 1] Hz (bottom). The highest frequency bin does not contain any emission. The red lines indicate the total contribution of the z ≤ 0.5 Universe. The high redshift contributions are small for the simple model we use and overall the signal is dominated by the z ≤ 2 Universe. The number of double WD, summed over redshift, that source the AGWB for the different frequency bins (top).