Lai (2006) 一文將利潤移轉效果納入傳統租稅競爭模型中發現：在三國兩廠商的架構下，當廠商進行數量競爭時，利潤移轉效果會讓租稅競爭的程度加劇，因此Oates (1972) 提出的假說仍然成立。本篇短文則發現Lai (2006) 所獲致的結果，廠商的家數扮演相當關鍵的角色。當本國廠商的生產成本為同質時，只要本國廠商相對競爭國廠商的家數夠多時，利潤移轉效果會緩和租稅競爭的程度而非加劇，且Oates (1972) 假說不一定會成立；當本國廠商的生產成本為異質時，配置生產效率效果會強化上述結果，使得租稅競爭的程度更為降低。

Under the three-countries-two-firms duopolistic structure, Lai (2006) incorporates the rent-shifting effect in the typical tax competition model. He finds that when firms compete in terms of quantity, the rent-shifting effect aggravates the under-provision of public goods in a Cournot duopoly, i.e., the Oates hypothesis still holds. However, in this note we find that the number of firms plays an important role in the result which Lai (2006) has obtained. Moreover, if the number of home country manufacturers is larger than the foreign country’s under the homogeneous cost structures of the home country manufacturers, the rent-shifting effect will increase (not reduce) the provision of public goods and mitigate (not aggravate) the inefficiency arising from tax competition. On the other hand, under the heterogeneous cost structures of the home country manufacturers, the effect of allocative production efficiency will enhance the above result.