From the results of a comprehensive asteroid population evolution model , we conclude that the YORP-induced rotational fission hypothesis can be consistent with the observed population statistics of small asteroids in the main belt including binaries and contact binaries .
The foundation of this model is the asteroid rotation model of , which incorporates both the YORP effect and collisional evolution .
This work adds to that model the rotational fission hypothesis , described in detail within , and the binary evolution model of .
The asteroid population evolution model is highly constrained by these and other previous works , and therefore it has only two significant free parameters : the ratio of low to high mass ratio binaries formed after rotational fission events and the mean strength of the binary YORP ( BYORP ) effect .

We successfully reproduce characteristic statistics of the small asteroid population : the binary fraction , the fast binary fraction , steady-state mass ratio fraction and the contact binary fraction .
We find that in order for the model to best match observations , rotational fission produces high mass ratio ( > 0.2 ) binary components with four to eight times the frequency as low mass ratio ( < 0.2 ) components , where the mass ratio is the mass of the secondary component divided by the mass of the primary component .
This is consistent with post-rotational fission binary system mass ratio being drawn from either a flat or a positive and shallow distribution , since the high mass ratio bin is four times the size of the low mass ratio bin ; this is in contrast to the observed steady-state binary mass ratio , which has a negative and steep distribution .
This can be understood in the context of the BYORP-tidal equilibrium hypothesis , which predicts that low mass ratio binaries survive for a significantly longer period of time than high mass ratio systems .
We also find that the mean of the log-normal BYORP coefficient distribution \mu _ { B } \gtrsim 10 ^ { -2 } , which is consistent with estimates from shape modeling ( ) .