原版P52：
The results  (3.20) and (3.22) are somewhat odd but play a crucial role throughout our analysis.They say that the size of the market affects neither the markup of price over marginal cost nor the scale at which individual goods are produced.As a result, all scale effects work through changes in the variety of goods available. obviously this is a rather strange result:Normally we think both that larger markets mean more intensive competition,and that one of the ways the economy takes advantage of the extent of the market is by producing at larger scale. The Dixit-Stiglitz model says, however, that all market-size effects work through changes in variety.

翻译（梁琦）：
方程(3.20)与(3.22)的结果有些出人意料，但是整个分析过程却是至关重要的。这表明，市场规模既不影响边际成本加成定价也不影响单一产品的生产规模，因此所有的规模效应都是通过产品种类的变化发生作用的。显然，这个结论非常怪异。我们一般认为，市场越大，竞争也就越激烈，而经济体利用市场优势的途径之一就是扩大生产规模。然而迪克西特-斯蒂格利茨模型却声称，所有的市场效应都是通过产品的种类变化起作用的。


“所有的规模效应都是通过产品种类的变化发生作用的”，这个结论如何通过式（3.20）与（3.22）得到？又该如何理解这个结论？