Surface number density profiles as a function of projected radius of open-cluster models at t = 100 Myr (left) and t = 600 Myr (right). Black curves show radial profiles of the surface number of density derived from two-dimensional observational data of stellar positions in the Pleiades (left; solid), Praesepe (right; solid), and Hyades (right; dashed). Error bars indicate the run-to-run variations.