從生產──分配鏈探討台灣汽、柴油市場的不對稱訂價

ASYMMETRIC PRICING IN THE GASOLINE AND DIESEL MARKETS OF TAIWAN

本文利用門檻共整合不對稱誤差修正模型，嘗試探索台灣氣、柴油價格與國際油價的關連。本研究將油價及匯率視為煉製汽、柴油的主要投入成本，並從生產──分配鏈區分兩階段價格傳遞機制，評估提煉及分配過程的價格不對稱。本文發現汽、柴油價格對負向成本衝擊有較明顯且迅速的反應，呈現「政治──經濟不對稱」。匯率衝擊則是主要的不對稱來源。比較不同之階段及油品的估計結果，我們推測生產與存貨調整成本、不完全競爭、及消費者搜尋等因素的確可能影響價格調整；然而，上游業者對「政治──經濟」的顧慮卻是主要支配力向。台灣汽、柴油的特殊訂價型態，其實隱含消費者可從中獲致更大利得。

This paper applies an asymmetric error correction model with threshold cointegration to explore the links between gasoline and diesel price adjustments in Taiwan and the prices of international oil. Oil prices and the exchange rate are the major input costs involved in refining gasoline and diesel. Upon examining the petroleum production-distribution chain, we assessed price asymmetry at the refinery and distribution stages. This paper finds that gasoline and diesel price adjustments follow a politico-economic asymmetry; that is, prices adjust more quickly to cost decreases than to cost increases. Exchange rate shocks are the main source of price asymmetry. By comparing kinds of gasoline, and stages in the production-distribution chain, we infer that asymmetry is caused by production and inventory adjustment costs, imperfect competition, and consumer search behaviors. It appears, however, that price adjustments are principally dominated by the political and economic concerns of the oil companies. Finally, we show that price asymmetry has a significant effect on consumer gains in Taiwan.