问题：为什么下列两个句子中than后补的谓语动词，一个放在主语前面，一个放在主语后面？

The mistakes children make in learning to speak tell linguists more about how children learn langrage than do the correct forms they used.
句中“the correct forms”与“the mistakes”比较，作主语；同时谓语动词“do”补在“the correct forms”前面。

Inflation has made many Americans reevaluate their assumptions about the future; they still expect to live better than their parents did, but not so well as they once thought they could.
句中“their parents”与“they”比较，作主语；同时谓语动词“did”补在“their parents”后面。

我觉得应该是比较的侧重点的不同。

比如说，The mistakes children make in learning to speak tell linguists

more about how children learn langrage than do the correct forms they used.

位于助动词补出出现在主语前，那就是一种倒装，倒装的目的就是强调，与后一句不倒装的谓语助动词侧重点就不同。

我觉得GMAT语法中没有考到助动词的位置，而是助动词是否出现。

以上都是个人观点，以前从来没有考虑过这个问题，我会再去查些资料。