Rate of orbital separation change compared to the rate of stellar mass change. In the gray shaded region, the mass of the donor star changes faster than the orbital separation while above (resp. below) the orbit expands (resp. contracts). The two limit cases are conservative mass transfer (dotted line, RLOF) and pure mass loss without accretion by the secondary (solid blue line). In-between, the solid green and red lines are for an accretion efficiency by the secondary of 5% and 50%, respectively. The arrows indicate that as mass transfer proceeds, the mass ratio can only decrease.