ellipsis - Repeating the verb in a comparison

Which of the following sentences are correct?

Mainlanders were actually more likely to be arrested than native Indians

Mainlanders were actually more likely to be arrested than native Indians were

Please explain.

Answer

Both sentences are correct and idiomatic, but the first (without “were”) is more common.

In English, there is a lot of flexibility as to what can be omitted. Usually everything that can be omitted is omitted. Here there is no ambiguity, so the verb does not convey any extra information, so the verb can be omitted, so the verb usually is omitted.

Here are some cases where the verb would be kept because it conveys some information.

It is usually said that Indians were often arrested in the 19th century, but studies show that this not true. Mainlanders are actually more likely to be arrested now than native Indians were [then].

Here the verb were indicates that the statement is about how likely Indians were to be arrested in the 19th century, not about how likely that would be now. If the sentence was just “… than native Indians”, then it would be ambiguous whether it was referring to Indians being arrested now or Indians being arrested in the 19th century. Adding “then” at the end is optional, but the sentence sounds better with it, to remind the reader why the past tense is used (because it refers to a time that was previously mentioned).

Mainlanders were actually more likely to see ghosts than native Indians were.

Here the verb “were” indicates that the sentence is about Indians seeing ghosts, not about mainlanders seeing Indians (which is what the sentence would mean without “were”).