Observable range of the best fitting inflaton potentials, when V(φ) is Taylor expanded to nth order around the pivot value φ_∗, in natural units (where assuming a flat prior on ϵ_V, η_V, , and , and using Planck+WP data. Potentials obtained under the transformation (φ − φ_∗) → (φ_∗ − φ) leave the same observable signature and are also allowed. The sparsity of potentials with a small V₀ = V(φ_∗) is explained by the flat prior on ϵ_V rather than on ln(V₀). In fact, V₀ is unbounded from below.