I can't find anything definitive about how many words they're 'supposed' to have at this age, and I'd find it really helpful to have some comparisons.
The backstory is that we adopted DD from foster care, where she was seriously under-stimulated. We've paid a lot of attention to language stuff to make up for it (nothing heroic, just lots of books, talking to her, reinforcing her babble, etc) and I'm interested to see how she's getting on.