Types of Investment

Economics

In economics, investment is the production per unit time of goods which are not consumed but are to be used for future production. Examples include tangibles (such as building a railroad or factory) and intangibles (such as a year of schooling or on-the-job training). In measures of national income and output, gross investment I is also a component of Gross domestic product (GDP), given in the formula GDP = C + I + G + NX. I is divided into non-residential investment (such as factories) and residential investment (new houses). "Net" investment deducts depreciation from gross investment. It is the value of the net increase in the capital stock per year.

Investment, as production over a period of time ("per year"), is not capital. The time dimension of investment makes it a flow. By contrast, capital is a stock, that is, an accumulation measurable at a point in time (say December 31st).

Investment is often modelled as a function of income and interest rates, given by the relation I = f(Y, r). An increase in income encourages higher investment, whereas a higher interest rate may discourage investment as it becomes more costly to borrow money. Even if a firm chooses to use its own funds in an investment, the interest rate represents an opportunity cost of investing those funds rather than loaning them out for interest.