This model examines the robustness of the growth cycle of Goodwin (196
7) when the effort level of the workers depends on the level of the re
al wage, using the Hopf bifurcation theorem. We show that if the effor
t level decreases as the real wage increase, this model gives rise to
a growth cycle, which is locally stable on the side of a unstable stat
ionary equilibrium under a technical condition. We also show that if t
he effort level depends positively on the real wage, then the stationa
ry equilibrium is stable.