The common phrases “in contrast” and “by contrast” are often changed by editors when these phrases form an introductory phrase in formal academic English. Some will change all instances of “in contrast” to “by contrast,” and others will change all instances of “in contrast” to “by contrast.” I fell into the second group of editors. My intuitive sense of native English does not agree with the term “by contrast.” However, it is best not to rely on intuition when editing, so recently, I investigated this issue, and this is what I found.
To my surprise, various Internet sources advise that “in contrast” is used with a preposition and “by contrast” is used at the beginning of a sentence with the subject of the sentence, that is,
“In contrast” is usually followed by “to” or “with” and requires a noun to follow it. “By contrast” is usually followed or preceded by the subject of the sentence. — Language Usage Weblog
…one sees both ‘in’ and ‘by contrast’. However, editors at the leading British scientific journal NATURE, always correct ‘in contrast’ into ‘by contrast’ . — English StackExchange
We can test the first assertion using the Google Ngram Viewer.
The Google Ngram Viewer tells us that “In contrast to” and “In contrast with” only make up 33.5% and 2.7% of all instances of “In contrast.” That leaves a sizable 63.8% of instances of “In contrast” that are not followed by “to” or “with.” Note that I’m presenting data for the capitalized versions “In contrast” and “By contrast,” assuming that this will return the instances that begin a sentence.
The Cambridge Dictionary gives different advice:
By contrast is less common than in contrast. We can use it alone or followed by with, but not by to. — Cambridge Dictionary
The Google Ngram Viewer partly supports this. “By contrast” is much less common than “In contrast.”
However, following “By contrast” by “with” or “to” is a slightly more complex story.
“By contrast with” makes up 1.8% of all instances of “By contrast,” but “By contrast to” to still makes up 1.1% of all instances.
The difference between them is not that great, and it is decreasing over time.
Of course usage, which is what the Ngram Viewer shows, isn’t the same as style. The Cambridge Dictionary may eventually decide that “by contrast to” is fine to use, but they haven’t yet. Moreover, if Nature prefers “by contrast” over “in contrast,” then they can certainly specify that in their journal style. However, a quick look at some of the usage examples found using Google Books shows that plenty of academic manuscripts do use “In contrast” followed by a comma. Hence, my editing advice is as follows:
- Use “in contrast” if a modern, native English style is requested by the client.
- “By contrast” is absolutely fine to use if preferred by the client.
- Change “by contrast to” to “in contrast to.”
- Change the introductory phrases “in contrast” to “by contrast” if the target journal is a Nature journal, just to be on the safe side.