Analyzing the Asymmetric Effect of Macroeconomic Variables on Food Prices in Iran

Introduction Food prices are an important indicator of societal well-being, and food inflation can deepen poverty in developing economies. Severe food price fluctuations not only affect food security in developing countries, but also affect economic growth and social stability. Any increase in food prices can push many people back below the poverty line. Rising food prices hit low-income households hard, as the household food basket accounts for nearly half of household living expenses. Therefore, food price stability is of particular importance to policymakers trying to lift households above the poverty line. Food prices in Iran have always been on the rise, and even in recent years, the rate of food price growth has accelerated. Today, inflation, especially food inflation, remains a major problem in Iran, and policymakers are always trying to reduce food inflation. In this regard, and with the aim of controlling food prices, different policies have been implemented in Iran, and the effectiveness of these policies has been discussed. Therefore, understanding the behavior of food prices in response to macroeconomic factors is essential for policymakers to implement appropriate policies at the right time and place to keep domestic prices stable. In this regard, in the present study, the asymmetric effect of macroeconomic variables (money supply, GDP per capita, exchange rate, and trade openness) affecting food inflation in Iran is examined using the nonlinear ARDL approach.   Materials and Methods The main objective of this study is to examine the asymmetric effect of domestic macroeconomic factors on food prices in Iran using a Non-linear Autoregressive Distributed Lag (NARDL) model. According to the theoretical literature, in this study, it is assumed that food prices are a function of macroeconomic variables, including money supply (MS), GDP per capita (GDPER), exchange rate (RATE), trade openness (OPEN), and global economic policy uncertainty index (EPU). Therefore, in accordance with Shin et al. (2014), the NARDL model used in this study is developed to examine the asymmetric effect of domestic macroeconomic factors (for example, money supply) as follows:   In the above relationship, each of the macroeconomic factors (including the money supply, GDP per capita, exchange rate, and trade openness) is separated into the sum of positive and negative components. In fact, two additional variables are created in each equation, one indicating an increase in the variable of interest with a positive sign and the other indicating a decrease with a negative sign. The variable of global economic policy uncertainty index also plays the role of a control variable. Due to the availability of data, the time period in this study is 1991 to 2022.   Results and Discussion The results of the linear and nonlinear bounds test in the ARDL model showed that there is a long-term relationship between macroeconomic variables including money supply, GDP per capita, exchange rate, trade openness, global economic policy uncertainty and food prices in Iran. In addition, the results of short-term and long-term symmetry tests using the Wald test showed that the effect of the exchange rate variable on food inflation in Iran is asymmetric in the long and short run, while the effect of the money supply and GDP per capita variables is asymmetric only in the long run; the effect of the trade openness variable is also symmetric in the short and long run and has a linear behavior. The results of the ARDL linear model estimation showed that in the short and long run, the effect of the growth of the variables of money supply, GDP per capita, exchange rate and global economic policy uncertainty on food inflation in Iran is positive and significant, while the effect of trade openness is negative and significant. The results of the NARDL model estimation also showed that the response of food inflation to increases and decreases in money supply and GDP growth is positive and significant, and their increase on food inflation is greater than the effect of their decrease. The response of food inflation in the long and short term to increases in the exchange rate is positive and significant, while the effect of decreasing the exchange rate in the long and short term is negative, but not statistically significant, and the effect of increasing the exchange rate on food inflation in the long term is greater than its effect in the short term. The effect of trade openness on food inflation is symmetric, with an increase in trade openness leading to a reduction in food inflation in both the short and long term.   Conclusion Linking the prices of agricultural products to market conditions and liberalizing the market for these products is an appropriate method for coordinating the effects of macro policies and specific agricultural policies that should be considered by policymakers. Given the importance of the agricultural sector, the government's economic policies in relation to food prices will be of high importance and sensitivity. Considering the results of implementing contractionary monetary policies in coordination with other Central Bank policies, increasing investment and efforts to increase productivity in the agricultural sector, appropriate foreign exchange policies are recommended to prevent unreasonable increases in the exchange rate, and reducing tariffs and trade restrictions to increase trade openness.