Posterior distribution of R2 burst rate and shape parameters. The blue contours indicate 1, 2, and 3σ upper limits on r and k. A lower k indicates a higher degree of clustering. The yellow region indicates the CHIME rate with Poissonian error bars. The red region is the CHIME rate modified by a spectral index of −3.6, where the CHIME lower limit on the rate matches the Apertif upper limit at k = 1, i.e. under the assumption of Poissonian statistics.