This line in my ~/.npmrc file has been killing my sanity for longer than I want to admit.
prefix=/Users/myusername/.nvm/versions/node/v10.0.0
If your globally installed npm binaries are not being found it could be because somehow you have a prefix set like the one above. I’m using nvm and I could not figure this out. All I had to do was delete this line and my binaries were finally installing in to the correct directory. I slayed the beast just now thanks to this handy issue comment.