It shows output, investment and depreciation as a function of the capital stock. The gap between the green line (investment) and the orange line (output) shows.We can apply the Solow model to specific cases, and use it to tell the story behind the economic growth that occurred. Solow sets up a mathematical model of long-run economic growth. He assumes full employment of capital and labor. Growth rate of output per person and capital per person is zero in steady state. This is the definition of steady state in Solow model. Capital share equals α, labor share equals 1−α in the model (always, not only along BGP). 5. The Solow Growth Model is an exogenous model of economic growth that analyzes changes in the level of output in an economy over time. Chapter 8 Economic Growth I: Capital.