在索洛看来，GDP增长率由土地、劳动力、资本等投入要素和全要素生产率共同决定。 全要素生产率（TFP）指不是因为投入量的变化、而是由于技术创新和制度改革所导致的产出变化。
For Solow, GDP growth is determined by the factor inputs of land, labor, and capital, together with the economy’s total factor productivity (TFP, or the change in output not accounted for by changes in the volume of inputs, but by factors like technological innovation and institutional reform).