Top: comparison of the Planck 2013 (blue points) and 2015 (red points) posterior-maximum low-ℓ temperature power spectra, as derived with Commander . Error bars indicate asymmetric marginal posterior 68% confidence regions. For reference, we also show the final 9-year WMAP temperature spectrum in light gray points, as presented by Bennett et al. (2013); note that the error bars indicate symmetric Fisher uncertainties in this case. The dashed lines show the best-fit ΛCDM spectra derived from the respective data sets, including high-multipole and polarization information. Middle: difference between the 2015 and 2013 maximum-posterior power spectra (solid black line). The gray shows the same difference after scaling the 2013 spectrum up by 2.4%. Dotted lines indicate the expected ± 1σ confidence region, accounting only for the sky fraction difference. Bottom: reduction in marginal error bars between the 2013 and 2015 temperature spectra; see main text for explicit definition. The dotted line shows the reduction expected from increased sky fraction alone.