颱風菜價與聯合行為之探討

在颱風天時，蔬菜價格偏高的情形時有耳聞，蔬菜市場價格甚至是產地價格的數倍，而蔬菜的頭尾兩端皆屬完全競爭市場，農民與消費者便是最大受害者。而當中導致價格上漲的原因有很多，而本文提出其中之一的原因交易成本來討論。消費者因防颱時間緊迫、和前往大賣場採購撲空的機會增大，或交通堵塞等情形，以致交易成本增大，使零售商可能趁機哄抬菜價，本文假設每位消費者都有不同的交易成本，在傳統市場與大賣場間做比價，藉由颱風天與普通天的交易成本不同，我們也可以成功解釋菜價劇烈波動的現象。在這個假設下我們可以提出減緩這些問題的可行做法。最後，政府可以藉由釋出蔬菜來減低消費者前往大賣場採購撲空的機率，又或者透過減少消費者交通不便等情形，藉由降低消費者買不到蔬菜的機率，確保蔬菜供應的穩定性與降低出門採購撲空的不確定性，可以更有效的抑制菜價上漲得情況。

關鍵字

交易成本；菜價；隱含式勾結；重複賽局

並列摘要

As you may know, the vegetable prices are getting high during typhoon period. The prices in vegetable market might even be several times of farm prices. The head and tail ends of vegetables from manufacturers to consumers are purely competitive market, farmers and consumers are the biggest victims by the price volatility, however, there are many reasons resulted in high vegetable prices, the research shown in this paper does focus on transaction cost which is one of reasons caused price volatility. Time might be running out to purchase goods at typhoon day, and customers most likely fail to buy food and supplies at hypermarket during this period, or they are impacted by traffic jams etc., transaction cost will be increased due to these factors, hence, retailers may take such opportunity to drive up the price of vegetable, assuming that each consumer has different transaction cost in this paper, not only compare the prices between traditional market and hypermarket, but also research different transaction costs between typhoon day and ordinary day, we are confident to explain the reason caused on volatility of vegetable prices. Under this assumption, we could raise feasible actions to mitigate those issues. Finally, either Government releases vegetable inventory to the market, it could reduce the chance that people fail to buy what they want in the hypermarket during typhoon season, or to improve traffic convenience, we expect it could lower the probability that insufficient vegetable supplied in the market. To conclude our opinion, ensuring stability on the supply of vegetables and reducing the uncertainty that people goes out but fail to purchase what they want are best efficient ways to restrain on raising price of vegetable.