Prediction of the binary period distribution (left panel) and mass-ratio distribution (right panel) for field F, G, K and M dwarfs on retrograde orbits. Expected binary fractions over the whole period range depend on spectral type and are indicated in the key. Every four neighbouring histogram bars with different filling patterns are in the same bin, whose centre is located in the middle between two integers in log₁₀P/d. For example, the centre of each of the four bars between log₁₀P/d = 2 and 3 is located at log₁₀P/d = 2.5 but is shifted against the others for the sake of visibility. While all sub-populations share the same initial period distribution (left panel, solid line), a common initial distribution for the mass ratio cannot be shown here since its shape depends on the spectral type (e.g. rising for M dwarfs over the whole q range but declining for F and G dwarfs for q ⪆ 0.4; Marks & Kroupa 2011). Thus, for example, ≈1% of all M dwarfs in the retrograde population are binaries with log₁₀P/d = 2 − 3 (left panel, black filled bar). All the retrograde M-dwarf binaries have a mass-ratio distribution shown by the black histogram in the right panel.