Time evolution of the dark matter bar strength parameter (A₂/A₀) in the x/y-plane, which compares the growth of the Fourier m = 2 mode to m = 0 mode for the three galaxy models. This measurement is taken for the slice of the halo ∣z∣ < 3 kpc within R < 12 kpc. Models are shown as (blue) circles for the prograde model, (black) diamonds for the nonrotating model, and (red) stars for the retrograde model.