【问】 They came earlier than expected.

than expected是省略形式，但省略掉的词语是什么呢?

【答】 语言学家们认为，这里省略了形式主语it和谓语动词was以及充当真实主语的动词不定式：

They came earlier than expected，=They came earlier than it was expected for them tocome.

You arrived earlier than necessary. =You arrived earlier than it was necessary for you to arrive.

类例：

1. The girls swam faster than was expected. (CGEL)

这些姑娘们游得比预料的快。

2. ...the result is better than could be expected(CGEL)

结果比可能预料的要好

(参见than¹)