Delirium wrote:
So I'd be surprised if we're "done" covering even the top-tier subjects before we get to 3 million articles, if even then.
After "size" (number of "real" articles), the next measurement must be "coverage". But how do we define that? Surely, coverage was 0% on the first day and will be 100% if Wikipedia can answer any possible question, but this is an unrealistic limit. Maybe Britannica is at 90% and Wikipedia at 80%? But we don't know how to define the "coverage" of an encyclopedia to begin with.
Corpus linguists first collect a very large body (a corpus) of text, then they count how many times each word occurs. If every 20th word (or 5% of the corpus) is "the", then a dictionary only containing "the" will "cover" 5% of this corpus. Most spelling dictionaries can cover 95-98 % of any normal corpus. But creating a dictionary that covers the last few percents is hard, because any normal text will contain a few very uncommon words. There is a very long, thin tail.
Could we compile a "corpus" of questions, and see how large a percentage of them can be answered by Wikipedia? That probably requires artificial intelligence, if not science fiction. (Hey, did somebody write a novel about this already? Sci-fi can be a great source of inspiration.) I guess we could compile a list of famous places and people, and see what percentage of them have articles of reasonable length. But having an entry on St Petersburg, Florida, is less important than having entries on London or Paris. So the list must be weighted. Search companies like Google or MSN keep logs of every query that people type in, so they know exactly how many times more often people search for London than for St Petersburg, Florida. That's the kind of weights we would need to compute a coverage, I guess.