Histograms for P ≥ 0.10. The frequency delta (f_Δ) histogram in the top panel shows a peak near zero, which means that many groups end at the same frequency in which they started. Data points under −22 d⁻¹ were added to an underflow bar. The frequency amplitude (f_A) histogram in the bottom panel shows that most groups show changes in frequency throughout their duration. Both f_Δ and f_A are described in Sect. 2.2.