Unlike in the Solow-Swan growth model, growth rate does not fall as the capital stock
increases in the Harrod-Domar Economic Growth Model for a production function
exhibiting a constant-returns-to-scale.
In the Harrod-Domar model, the growth rate is determined by the savings rate and the capital-output ratio, rather than the level of capital stock. This is because the model focuses on the importance of investment in driving economic growth, rather than the diminishing returns to capital as in the Solow-Swan model.
In a production function exhibiting constant returns to scale, the additional units of capital will lead to proportionate increases in output, leading to a constant growth rate. This means that as the capital stock increases, the growth rate remains the same, reflecting the idea that investment in capital is essential for sustained economic growth in the Harrod-Domar model.