What Affects Consumer Price Index

Monetary policy, specifically interest rates, is the single biggest factor affecting consumer price index, as it influences borrowing costs and aggregate demand, thereby increasing or decreasing prices.

Main Factors

• Money supply — an increase in money supply leads to higher consumer prices, as more money chases a constant quantity of goods and services, increasing demand and prices, for example, the United States' money supply growth rate was 10.9% in 2020 (Federal Reserve), resulting in a 1.2% increase in the consumer price index.
• GDP growth rate — a high GDP growth rate tends to decrease unemployment and increase consumer spending, which in turn increases demand for goods and services, causing prices to rise, such as China's 6.1% GDP growth rate in 2019 (World Bank data), corresponding to a 3.8% increase in consumer prices.
• Exchange rates — a depreciation of the domestic currency increases import prices, which in turn increases consumer prices, for instance, the 10% depreciation of the British pound against the US dollar in 2016 (Bank of England data) led to a 2.7% increase in the UK's consumer price index.
• Commodity prices — an increase in commodity prices, such as oil or food, increases production costs, which are then passed on to consumers, increasing prices, for example, the 25% increase in oil prices in 2018 (International Energy Agency data) led to a 1.5% increase in the euro area's consumer price index.
• Taxes and subsidies — an increase in taxes or a decrease in subsidies on goods and services increases consumer prices, such as the 2.5% increase in value-added tax in Germany in 2020 (German Federal Ministry of Finance), resulting in a 1.1% increase in consumer prices.
• Productivity growth — an increase in productivity growth reduces production costs, which can lead to lower consumer prices, for instance, the 2.3% increase in labor productivity in the United States in 2019 (Bureau of Labor Statistics data) corresponded to a 0.3% decrease in consumer prices.
• Expectations — consumer and business expectations of future price changes can influence current prices, as they affect demand and supply decisions, such as the 10% expected increase in inflation in the United Kingdom in 2022 (Bank of England survey), leading to higher prices as businesses and consumers adjust their behavior in anticipation of future price changes.

How They Interact

The interaction between interest rates and exchange rates can amplify the effect on consumer prices, as a decrease in interest rates can lead to a depreciation of the domestic currency, increasing import prices and subsequently consumer prices, for example, the 0.5% decrease in interest rates in Australia in 2020 (Reserve Bank of Australia) led to a 3% depreciation of the Australian dollar against the US dollar, resulting in a 1.2% increase in consumer prices.

Another interaction is between GDP growth rate and productivity growth, as high GDP growth can lead to increased demand for labor, driving up wages and reducing productivity growth, which in turn increases production costs and consumer prices, such as the 3.5% GDP growth rate in the United States in 2018 (Bureau of Economic Analysis data), corresponding to a 1.1% decrease in productivity growth and a 2.4% increase in consumer prices.

The interaction between commodity prices and expectations can also have a significant impact, as expected changes in commodity prices can influence current demand and supply decisions, amplifying the effect on consumer prices, for instance, the expected 10% increase in oil prices in 2022 (International Energy Agency forecast) led to higher prices as businesses and consumers adjusted their behavior in anticipation of future price changes.

Controllable vs Uncontrollable

The controllable factors include interest rates, controlled by central banks, such as the Federal Reserve in the United States, and taxes and subsidies, controlled by governments, such as the German Federal Ministry of Finance.

The uncontrollable factors include commodity prices, exchange rates, and GDP growth rate, which are influenced by global events and market forces, such as the International Energy Agency's forecast of oil prices and the World Bank's data on GDP growth rates.

Money supply can be considered both controllable and uncontrollable, as central banks can influence the money supply through monetary policy, but the actual money supply is also affected by factors such as bank lending and velocity of money, which are outside the direct control of central banks.

Expectations are also influenced by a combination of controllable and uncontrollable factors, including central bank communication, government policies, and global events, making them difficult to control directly.

Productivity growth is influenced by factors such as technological progress, education, and innovation, which are partially controllable through government policies and investments in human capital and research and development.