Measurements of the double-differential thick-target neutron yield are made for 75- and 120-MeV 12C5+, 153-MeV 16O5+, and 40-MeV alpha particles bombarding carbon, aluminum, copper, and lead targets. The measured data are parameterized by using the two-component moving source model. The systematic variation of the equilibrium neutron (EN) yield with incident ions and targets is analyzed by using the thus-obtained moving source parameters, and a simple expression is proposed to describe the systematics in the EN yield. The systematic change in the nonequilibrium neutron (NEN) yield was formulated to a simple expression by using the local hot spot model. The proposed expression reproduced well the measured EN and NEN yields.