Asymmetric Price Transmission in Bangladesh's Egg Markets: ARDL– NARDL Evidence and Welfare Implications
This study utilizes ARDL and NARDL models on Bangladesh's egg market data from 2000 to 2024 to demonstrate that asymmetric price transmission, where rising costs pass through faster than falling ones, undermines food security and equitable welfare, thereby necessitating targeted policy interventions to advance sustainable development goals.
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
In the bustling markets of Bangladesh, where families rely on affordable food to survive, the price of a simple egg tells a complex story about how money moves through a nation. For decades, economists have understood that in a perfectly fair and efficient market, prices should behave like water in a connected system: if the cost rises in one city, it should rise in another, and if it falls in one, it should fall in the other at the same speed. This idea, known as the Law of One Price, suggests that traders and transporters act as a single, fluid network, smoothing out differences so that no one region is left paying too much or too little for the same goods. However, real-world markets are often messy. When intermediaries hold power or when information is scarce, prices can get stuck, rising quickly when costs go up but refusing to fall just as fast when costs drop. This phenomenon, where prices shoot up like a rocket but drift down like a feather, creates a hidden tax on the poorest consumers, transferring wealth from their pockets to the hands of traders.
A team of researchers from Bangladesh and Australia set out to see if this unfair pattern was happening in the country's egg markets. They gathered twenty-five years of monthly price data from seven major cities, stretching from the capital, Dhaka, to the remote northeastern market of Sylhet. Using advanced statistical tools designed to detect subtle, one-sided behaviors in data, they mapped how price changes traveled across the country. They found that while the markets are indeed well-connected, with prices in all seven cities moving together in the long run, the speed of that movement is deeply uneven. When the price of eggs went up in Dhaka, it surged quickly to the regional markets. But when the price dropped in the capital, the relief trickled down to the countryside much more slowly. This asymmetry means that for years, consumers in these regions have been paying more than they should have, a pattern that holds true regardless of the distance from the capital or the time of year.
The study, which analyzed 300 monthly observations for each of the seven regional markets, confirmed that the egg markets of Bangladesh are fully integrated, meaning they function as a single national system rather than isolated pockets. Yet, this connection does not guarantee fairness. The researchers discovered that the speed at which prices adjust depends heavily on the direction of the change. In every single pair of markets they compared, positive price shocks traveled faster than negative ones. For instance, a ten percent increase in the price of eggs in Dhaka eventually led to a nearly ten percent increase in the price in Gazipur, but a ten percent decrease in Dhaka resulted in only an eight percent drop in Gazipur. This gap, where the full benefit of lower costs never reaches the consumer, is the mathematical signature of the "rockets and feathers" effect. The researchers also identified Dhaka as the dominant leader of the market; prices in the capital drive the changes, while the regional markets follow, though they often lag behind when it comes to passing on savings.
Beyond the mechanics of price movement, the study calculated the human cost of this imbalance. By simulating how these price patterns affect household budgets, the researchers estimated that the slow downward adjustment of prices has cost consumers hundreds of millions of dollars in lost value over the last two and a half decades. This loss is not shared equally; it falls heaviest on the poorest families, who spend a much larger portion of their income on food than the wealthy. For the bottom income groups, who already struggle to afford enough protein, this hidden inefficiency acts as a regressive tax, taking money away from those who can least afford to lose it. The findings suggest that while the physical infrastructure of the market is working well enough to connect the country, the economic rules governing how prices move are tilted against the consumer.
The researchers also looked at how major events, such as the global food crisis of 2008, bird flu outbreaks, and the pandemic, disrupted these patterns. They found that while these shocks caused temporary spikes and breaks in the data, the underlying asymmetry remained stubbornly consistent. Even as roads improved and mobile phones brought better information to rural traders, the tendency for prices to rise fast and fall slow did not disappear. In fact, the gap between how quickly prices rise versus how slowly they fall seemed to widen slightly in the most remote markets, suggesting that distance and a lack of competition allow traders to hold onto their margins for longer. The study concludes that fixing this issue requires more than just building better roads; it demands active market surveillance and policies that ensure price signals are transmitted fairly in both directions. Without such intervention, the promise of a connected, efficient market remains incomplete, leaving the most vulnerable households to pay the price for a system that works perfectly for everyone else.
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