Capital income is calculated using which formula?

Capital income is derived from the marginal product of capital (MPK) multiplied by the quantity of capital (K). This relationship highlights how much additional output (income) can be produced from an additional unit of capital while holding other factors constant. In this formula, the concept of alpha (α) often represents the share of income attributed to capital in the total output (Y).

Understanding this formula is crucial because it reflects the income generated directly from the productive use of capital in the economy. In macroeconomic theory, the distinction between the contributions of capital and labor to total output is fundamental, as it provides insights into how economies grow and how different factors contribute to income distribution.

The other options either focus on labor or attempt to combine the contributions of both capital and labor without isolating capital income specifically, which is critical for analyzing capital's role in generating income.