Distribution of the ratio q between the observed extrema of mean magnetic field moduli of the 66 Ap stars with resolved magnetically split lines presently known for which more than one measurement of ⟨ B ⟩ is available. Although HD 96237 was observed twice by Freyhammer et al. (2008), its spectral lines were not resolved in the first epoch spectrum. The shaded part of the histogram corresponds to those stars that have been observed throughout their rotation cycle (see text).