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。
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