Fiscal-Monetary Policy Interactions and Macroeconomic Transmission under Exogenous Shocks: A HANK Approach
This paper utilizes a heterogeneous-agent New Keynesian (HANK) model to demonstrate that the macroeconomic and distributional effects of fiscal-monetary policy interactions under exogenous shocks are fundamentally shaped by the specific nature of the shock and household heterogeneity, particularly through the amplifying role of liquidity-constrained consumers.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Economics often feels like a study of averages, where the behavior of a single "representative" person is used to predict how an entire nation will react to a change in taxes or interest rates. In this simplified view, everyone is assumed to have the same ability to save money, the same access to loans, and the same reaction to a pay cut. However, the real world is far more uneven. Some households live paycheck to paycheck, with no savings to fall back on, while others hold significant wealth and can smooth out their spending even when times are tough. This difference in financial resilience is crucial because it changes how money moves through the economy. When a government tries to stabilize the economy after a shock, such as a sudden rise in prices or a drop in productivity, the outcome depends heavily on whether the people affected can borrow money to keep spending or if they are forced to cut back immediately. Understanding these differences is essential for predicting whether a policy will work or if it will accidentally make things worse.
In a recent study, researcher Min Gyu Lee explores exactly how these differences in household wealth interact with the rules that governments and central banks follow. The study uses a sophisticated computer simulation to model an economy where people are not all the same. Instead of assuming one average citizen, the model includes a wide variety of households, some with deep pockets and others who are financially fragile. The researchers programmed the government to follow specific, predictable rules: when the economy slows down or debt rises, taxes automatically adjust, and government spending changes to keep the budget balanced. The central bank was also programmed to follow a standard rule, raising or lowering interest rates based on how fast prices are rising and how the economy is growing. The goal was not to find the perfect, theoretical policy, but to see what actually happens when these two authorities follow their standard rules while facing unexpected economic storms.
The simulations tested three main types of economic shocks. The first was a "cost-push" shock, where the cost of making goods suddenly goes up, forcing prices higher. The second was a drop in productivity, where workers become less efficient. The third was a shock to government debt, representing a sudden need to issue more bonds or pay them down. The results revealed that the type of shock matters immensely. When the economy faced a cost increase or a sudden rise in debt, the government's automatic response was to raise taxes and cut spending to protect its long-term financial health. This might seem harsh, but in the simulation, it forced the economy to adjust quickly. Surprisingly, this fiscal tightening did not crush investment. Because the government spent less, more resources were left available for private companies to build factories and buy equipment. This created a "crowding-in" effect, where private investment actually grew even as the rest of the economy shrank.
However, the story changed when the shock came from a drop in productivity. In this scenario, the economy did not just slow down; it entered a recession driven by a collapse in demand. Because many households in the model had no savings, a drop in their wages meant they had to stop spending immediately. This sudden halt in spending caused prices to fall, creating a deflationary spiral. The central bank tried to help by lowering interest rates, but the drop in prices was so severe that the real cost of borrowing actually went up, making it harder for businesses to invest. In both cases, the presence of households with no savings made the economic downturn much deeper and faster than it would have been if everyone had been able to save and borrow freely.
The study also looked at what happens when the economy gets a boost, such as when technology improves or costs go down. In these good times, the government's rules led to a different outcome. With more money flowing in, the government cut taxes and increased spending. This extra cash went directly to households, many of whom spent it immediately. This surge in consumer spending was so strong that it actually crowded out private investment. Because so much of the economy's output was being used for current consumption and government projects, there was less left over for businesses to invest in the future. This finding challenges the idea that a booming economy always leads to more investment; instead, it suggests that if the government and consumers spend too much of the new wealth right away, businesses may actually cut back on their long-term plans.
One of the most significant findings of the research is that the standard way of looking at the economy often misses these critical details. When the researchers compared their model with one that assumed everyone was the same, the standard model predicted a much milder reaction to shocks. It failed to see the depth of the crash because it assumed that people could easily borrow money to keep spending when their wages dropped. The simulation with diverse households showed that when the most vulnerable people are forced to stop spending, the entire economy suffers a much sharper decline. This suggests that policies designed to stabilize the economy must account for the fact that some people cannot wait for things to get better; they need help immediately, or the damage to the economy will be far greater than expected.
The study concludes that the interaction between fiscal and monetary policy is not a fixed recipe but a dynamic response that changes depending on the nature of the problem. There is no single "best" way to handle a crisis. If the problem is a supply shock or a debt issue, the automatic response of raising taxes and cutting spending can actually help stabilize the economy by freeing up resources for investment. If the problem is a drop in productivity, the same rules can lead to a severe demand collapse. The research highlights that the health of the economy depends as much on the distribution of wealth among households as it does on the interest rates set by the central bank. By understanding how different groups react, policymakers can better anticipate the ripple effects of their decisions, ensuring that the tools they use to fix the economy do not inadvertently make the most vulnerable people suffer the most.
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