| 摘要: | 現今許多產業生產活動會製造出大量污染物質，政府為了解決環境污染問題通常會訂定相關的環境政策使污染外部性內部化，使環境污染廠商負擔生產所造成的負外部成本，進而讓製造污染廠商考慮環境污染問題。本文假設在上、下游供應產鏈中，上游為獨占之公營廠商，下游為寡占之民營廠商，下游製造一單位的最終財會使用到一單位的中間財，而兩下游民營廠商會生產同質產品，雖兩家下游民營廠商生產成本相同，但因為下游民營廠商重視污染程度不同，因此生產總成本會隨著不同的污染排放量而有所差異，另外因完全公營廠商在現實中較為罕見，因此會多加探討上游公營廠商在不同民營化程度下的最適中間財價格決策以及如何影響下游民營廠商的生產決策，藉由以上假設，建構出多階段賽局。
在上游為完全公營廠商下，當下游污染越嚴重，最適中間財價格會越高，而政府課徵之污染稅會與上游最適中間財價格呈反向關係，而政府課徵污染稅只會影響下游民營廠商之個別產量，下游污染越嚴重，個別產量越低，對最終財市場總產量及市場價格無影響，因此，在上游為完全公營的情況下，政府污染稅越高，社會福利也越高。
若上游部分民營化後，當上游為完全民營化且最適污染稅不為零下，下游個別廠商的生產策略會依照下游民營廠商污染排放量及邊際污染損害大小而定，若上游同樣為完全民營廠商但最適污染稅為零時，當下游污染情況越嚴重，下游民營廠商之個別產量也會越少，整體最終財市場產量會減少，市場價格提高，不利於社會福利極大化。
;Nowadays, many industrial production activities cause large amount of pollutants. In order to solve the problem of environmental pollution, the government usually formulates environmental policies to internalize the externality of pollution, so that polluting manufacturers must pay attention to solving the pollution problems. This paper assumes that in the supply chains, the upstream is a monopoly public firm, and the downstream are two oligopoly private firms. The downstream manufacturers produce one unit of final goods will use one unit of intermediate goods, while the two downstream private firms will produce homogeneous products. Although the production costs of the two downstream private firms are the same, the downstream private firms pay attention to the different degree of pollution. Therefore, the total production cost will vary with different pollution emissions. In addition, because the completely public firms are rare in reality, we will additionally discuss about the optimal intermediate goods price decisions of upstream public firm under different degrees of privatization and how it affects the production decisions of downstream private firms. Based on the above assumptions, a multi-stage game will be constructed.
As the upstream is a completely public firm, the downstream firms produce more pollution, the price of the optimal intermediate goods will be higher, and the pollution tax imposed by the government will be lower. Furthermore, the pollution tax imposed by the government will only affect the individual output of downstream private firms, the more pollution that private firms made, the lower of the private firms individual output produce, which has no impact on the total output and market price of the final product market. Therefore, in the case where the upstream is completely public, the higher of the government pollution tax, the higher of the social welfare.
As the upstream become partially privatized. When the upstream is completely privatized and the optimal pollution tax is greater than zero, the production strategy of individual downstream manufacturers will be determined by the pollution emissions and marginal pollution damage of the downstream private firms. However, when the optimal pollution tax is equal to zero, the more pollution made by downstream, the smaller of the downstream private firms output, the overall of the final product market output will decrease, and the market price will increase, which is harmful to the maximization of social welfare. |
