Joy’s law obtained by the binned fitting method. The upper panels show the linear fitting and the lower panels show the square-root fitting. The left column is based on DPD_all with Δs ≥ 0° and the right column is based on DPD_max with Δs ≥ 0°. Cycles 21 to 24 are shown in black, red, blue, and green, respectively. The dashed lines show the fitting result of the average values in 5° latitude bins by the least square method (the last bin contains data with latitudes greater than 30°). The error of the mean is the standard deviation of the bin sample divided by in each bin.