Peto logrank pvalues as a function of the number of upper limits (in percentage with respect to the total sample size). From the 5BZCat redshift sample, two subsamples of equal size were extracted: the first is kept unmodified (only measurements), in the second a progressively larger number of measurements were flagged as UL. In this way, the second subsample includes both measurements and censored data. The Peto logrank test was applied to subsamples of the same size at each step. The results for subsample size =20 in blue, 50 in orange, 100 in green, and 200 in red are shown by plotting, for each case, the median of the pvalues obtained over 100 realizations.