where formula_27 is the amount of investment decisions in fixed capital, formula_28, formula_29 and formula_30 are parameters that specify a linear relation, formula_31 is a constant which can vary in the long-run, formula_1 are profits, formula_7 is the gross saving generated by the firm, and formula_34 is the stock of fixed capital. The equation shows that investment decisions depend positively on savings generated by the firm, the rate of change of profits, a constant which is subject to long-term changes, and negatively on the increase of fixed capital.