4.1.2. Investment

Investment is defined as addition to the stock of physical capital (such as machines, buildings, roads etc., i.e. anything that adds to the future productive capacity of the economy) and changes in the inventory (or the stock of finished goods) of a producer. Note that ‘investment goods’ (such as machines) are also part of the final goods – they are not intermediate goods like raw materials. Machines produced in an economy in a given year are not ‘used up’ to produce other goods but yield their services over a number of years.

Investment plays a crucial role in enhancing the productive capacity of an economy. It refers to the increase in physical assets like machinery, buildings, and infrastructure that contribute to future production. Unlike intermediate goods, which are used up in the process of creating other goods, investment goods, like machines, last longer and enable producers to generate goods and services over time.

Consider a bakery that decides to buy a new oven. This oven represents an investment because it is a physical asset that will help the bakery produce more bread and pastries in the future. Instead of being consumed immediately, this investment will generate profits and products over several years.

Investment decisions by producers, such as whether to buy a new machine, depend, to a large extent, on the market rate of interest. However, for simplicity, we assume here that firms plan to invest the same amount every year. We can write the ex ante investment demand as I = I.

Producers often weigh the costs and benefits of investing, which can include analyzing interest rates. Higher interest rates make borrowing costs more expensive, potentially dissuading investment. For simplification in this context, it's assumed that firms will consistently invest a set amount each year, represented by an equation like I = I, indicating predetermined investment levels.

Imagine a tech company considering whether to invest in new software. If the interest rates for loans are low, it may decide to invest heavily in the software as the cost of borrowing money is less. In contrast, at high interest rates, the company might hold off on the investment, waiting for a more favorable economic environment.

We can write the ex ante investment demand as I = I (4.2) where I is a positive constant which represents the autonomous (given or exogenous) investment in the economy in a given year.

Ex ante investment refers to the planned amount of investment that businesses intend to undertake within a certain period, based on their expectations. In contrast, ex post investment represents the actual investment made at the end of that period. Understanding this distinction is essential for economic analysis, as planned investments can differ significantly from actual outcomes due to market fluctuations.

Think of a farmer who plans to invest $10,000 in new equipment for their farm (ex ante). However, due to unexpected weather conditions and lower crop yields, they only spend$7,000 (ex post). This scenario illustrates how planned investments may not always translate to actual investments.

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