Multiplicity and stagnation under the Romer model with increasing returns of R&D

This study develops a simple growth model to explain stagnation and non-simple growth patterns by using increasing returns of R&D efficiency. The study adopts a type of the lab-equipment model, namely, the Romer model, where goods are used as R&D input. Here, we assume capital, or durable goods, as the R&D input factor, and R&D efficiency is assumed to be variable. This arrangement yields three steady states, namely: no-growth, low-growth, and high-growth steady states. These trajectories are jumpable. Accordingly, global indeterminacy is obtained. By uniting the numerical analysis, we obtain that all steady states are saddle stable. However, when the increasing R&D efficiency is small, the path converging to a high-growth-rate steady state shows local indeterminacy.