Line densities as a function of redshift for low-ionisation lines. In all panels, coloured symbols represent the JWST data, where error bars for the line densities represent 68% confidence intervals for small-number Poisson uncertainties (Gehrels 1986). The line densities are compared to predictions from numerical models (Huscher et al., in prep.) computed from the same selection of W_r as from the NIRSpec observations. Upper left panel: O Iλ1302 absorption line densities for systems with W_r > 0.05 Å showing an increase in line density at z > 6.5 from the NIRSpec data compared to lower redshifts (Becker et al. 2019). Upper right panel: C IIλ1334 absorption line densities for systems with W_r > 0.03 Å compared to lower redshift values derived from the catalogue in Davies et al. (2023b). Lower left panel: Si IIλ1526 absorption line densities for systems with W_r > 0.025 Å compared to that derived from the absorption database in Davies et al. (2023b). The model prediction at dn/dX ≈ 0.04 under-produces the Si II line densities by a factor of ≈12. Lower right panel: Mg IIλ2796 absorption line densities for systems with W_r > 0.3 Å. Compared to the Mg II study in (Chen et al. 2017), the NIRSpec data suggest that the line density could be constant or have a shallow decrease with increasing redshifts in agreement with the model prediction.