Argue away!Sorry to argue with elroy but it sounds quite formal to me and is used in Australia to sound more elegant than 'a lot of'.
I would never mark it as being informal.
Elroy,Well, yes. No one's saying it doesn't mean that. We just have different opinions about when we'd use it.
what does the learner of English do here?
I will happily bow to you on that one.It does not surprise me that there are more Google hits for "a great deal of" than "a great amount of." I reckon there is a great deal of informal and not-so-formal junk on the Internet, and not such a great amount of formal pronouncements.
We are talking about "deal" as meaning "a usually large or indefinite quantity or degree". MW does not mark this usage as informal, nor does Cambridge. I haven't found any information yet about when or how "deal" came to have this meaning. Have you found any source that marks it as informal?It is not always possible to universally categorize a word or phrase according to its degree of formality, which is often subject to convention, idiosyncrasy, and regional preferences. If learners could just rely on Collins to resolve these issues by assuming that any entry without a usage label is formal by default, there would be no point in coming here to ask.
Actually, we have not established that, not yet. We have a few opinions, no mention of any dictionary specifically marking "a great deal of" as being informal or something to be avoided for any reason.We have already established that "a great deal of" is informal in the US but apparently more formal in Australia.
Anyone who would grade you poorly for using "a great deal of" would be astoundingly ignorant. God save us all from people who spend more time telling people how to write than reading!My opinion is not only based on the poor grade I might receive if I used "a great deal of" in a formal essay or paper. I cannot imagine myself preparing a formal speech and using "a great deal of." It just doesn't seem to fit in that register.