Sketch of the forecasting steps and choices for the stage IV configuration. We explored fewer redshift nuisance models here than for the stage III configurations, since the n(z) biases described in Sect. 3.2.1 are comparatively simple, only featuring shifts in the tomographic mean redshifts that ought to be well compensated for by the δz_i model. In addition, results from stage IV forecasts are always considered on the σ₈ − Ω_m plane given that cosmic shear alone has sufficient constraining power to alleviate the non-linear degeneracy seen for stage III.