*Article* **Incorporating Fuzzy Logic in Harrod's Economic Growth Model**

**Joan Carles Ferrer-Comalat 1,\*, Salvador Linares-Mustarós 1 and Ricard Rigall-Torrent 2**


**Abstract:** This paper suggests the possibility of incorporating the methodology of fuzzy logic theory into Harrod's economic growth model, a classic model of economic dynamics for studying the growth of a developing economy based on the assumption that an economy with only savings and investment income is in equilibrium when savings are equal to investment. This model was the first precursor to exogenous growth models, which in turn gave rise to endogenous growth models. This article therefore represents a first step towards introducing fuzzy logic into economic growth models. The study concerned considers consumption and savings to depend on income by means of uncertain factors, and investment to depend on the variation of income through the accelerator factor, which we consider uncertain. These conditions are used to determine the equilibrium growth rate of income and investment, as well as the uncertain values for these variables in terms of fuzzy numbers. As a result, the new model is shown to expand the classical model by incorporating uncertainty into its variables.

**Citation:** Ferrer-Comalat, J.C.; Linares-Mustarós, S.; Rigall-Torrent, R. Incorporating Fuzzy Logic in Harrod's Economic Growth Model. *Mathematics* **2021**, *9*, 2194. https:// doi.org/10.3390/math9182194

Academic Editors: Jorge de Andres Sanchez and Laura González-Vila Puchades

Received: 29 June 2021 Accepted: 6 September 2021 Published: 8 September 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

**Keywords:** fuzzy logic; fuzzy arithmetic; extension principle; economic models; Harrod's growth
