Der Begriff Investitionsfunktion erklärt die Abhängigkeit der Investitionen von verschiedenen Einflussfaktoren, darunter vom Zinsniveau. Der Zusammenhang ist deshalb von besonderem Interesse, weil die Zentralbank die Höhe der Zinsen und damit die Cost of capital von Investitionen direkt beeinflussen kann. Denn diese werden überwiegend über Kredite finanziert.
As a rule, it is assumed that the macroeconomic investment quota decreases when interest rates rise and increases when interest rates fall. In addition to the level of interest, it is primarily profit expectations, corporate taxes and confidence in the economic future that determine whether investments are made and whether investments are postponed or rejected.
Changes in national income also influence an economy's investment rate. With it the total demand and thus the total production rise or fall. In order to meet the increased demand, many companies will invest additionally. On the other hand, if overall demand falls, investment activity will decline.
This connection has led to an important macroeconomic variable in economic theory, the accelerator.
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