Long-term changes in the KSO differential rotation parameters. In the top panel SILSO sunspot group numbers are shown in phase space, where the whole phases mark cycle minima. Phase range 0–1 belongs to SC 20, phase range 1–2 to SC 21, etc. Phase 0 indicates the beginning of the analysed time period (1964). A LOESS non-parametric fit was applied to the original data using span = 0.65, and a smoothing in a window covering 65% of data points (red curve) in order to obtain general trend. The same was performed for parameters A and B (middle and bottom panel), but with moving-average values in order to remove in-cycle variations, with a LOESS smoothing of the same span as before. Moving averages were calculated over two solar cycles for each of the data points, which corresponds to the periodicity of parameter A.