Is "more importantly" good English?

I was taught in school in the UK that it was either "more important" or "importantly," never "more importantly." We say "interestingly" or "more interesting," not "more interestingly".

Is "more importantly" good English?

Solution 1:

Comparing levels of importance and interest seems normal on its face. I assume Paul Brians earned his stripes to become Emeritus Professor of English Washington State University, but it seems his prescriptive opinion about leading with a sentence adverb has been overruled by Everyman:

When speakers are trying to impress audiences with their rhetoric, they often seem to feel that the extra syllable in “importantly” lends weight to their remarks: “and more importantly, I have an abiding love for the American people.” However, these pompous speakers are wrong. It is rarely correct to use this form of the phrase because it is seldom adverbial in intention. Say “more important” instead. The same applies to “most importantly”; it should be “most important.”

There may be certain situations where combining the comparative adverb more with the adverb importantly does not make sense, but that prohibition generally defies grammatical definition. As an adverb, more is an extremely flexible modifier:

a word that modifies a verb, adjective, other adverb, determiner, noun phrase, clause, or sentence...

Adverbs are traditionally regarded as one of the parts of speech. However, modern linguists note that it has come to be used as a kind of "catch-all" category, used to classify words with various different types of syntactic behavior, not necessarily having much in common except that they do not fit into any of the other available categories (noun, adjective, preposition, etc.)

The prohibition also flies in the face of conventional usage:

See the usage graph for more importantly.

A similar graph appears for more interestingly.

It seems that this prohibition was enforced until the 1940's when more importantly started to break out of the prescriptive box. By the turn of the millennium, more interestingly was 8 times more popular than in 1940. More importantly was 35 times more popular. More interestingly still seems a bit awkward, but more importantly is ubiquitous 15 years later.

More important/interesting works in some situations. More importantly/interestingly works in other situations. Leading with a sentence adverb was once considered pompous, but the expression has scored a reversal, and the prohibition is now pure pretension.

public.wsu.edu/~brians/errors/importantly.html

www.oxforddictionaries.com

en.wikipedia.org

Solution 2:

I think the origin of the prohibition against "more importantly" may be that when it comes at the beginning of sentences, importantly is not used as a sentence adverb. The reasoning is that if it's not grammatical, putting more in front of it shouldn't make it grammatical. People don't say

Importantly, we need to figure out how to pay the rent.

So the idea was that if we can't start a sentence with "Importantly", we shouldn't be able to start one with "More importantly". We should use "More important" because it's an ellipsis for a phrase like "What is more important ...".

Since we can use "Interestingly" at the beginning of a sentence, we should be able to use "More interestingly". On the other hand, since we can also use "What is more interesting ...", there's nothing ungrammatical about starting a sentence with "More interesting".

Nobody should ever have objected to "more importantly" in sentences like:

This issue, bearing so importantly on our economy and even more importantly on our system of education, ...

So what do I think?

There is a good argument that as a sentence adverb, more importantly is ungrammatical, and indeed Ngrams shows it wasn't used in the 19th century.

The same argument says that more interestingly is indeed grammatical. (Unless you want to say that interestingly is not a valid sentence adverb; it wasn't in the 19th century, but it is now. See these two Ngrams).

However, the usage of more importantly is already well-established, so any crusade against it is a losing cause.