Impact of the n_s prior: Comparing marginalised posterior distributions for the BOSS galaxy clustering analysis for our fiducial analysis (blue) with the constraints when adopting an uninformative prior on n_s (orange). Opening the parameter space to arguably unphysical values of n_s favours higher values and weaker constraints on Ω_m. Constraints on S₈ are, however, fairly insensitive to the choice of n_s prior.