I have searched several websites, including this forum, for finding information about using a negative clause after "not only." I found that in most cases it's not ungrammatical to use a double negative in "not only...but also". Still, the following sentence seems awkward and ungrammatical to me. Please let me know if it is incorrect, and if yes, how can I rephrase it?
"Not only did the economic growth rate not rise, but it fell."