Where are they getting public domain opinions that CL doesn't have? Are these states or counties that CL doesn't scrape? It would be nice to have a breakdown by jurisdiction.
Also, by "case" do you mean "opinions"?
Full disclosure, I've written and contributed to several scrapers for CL, and if there's a large source they're missing I'd like to know.
Note that the CL opinion number you're quoting doesn't include orders from Federal courts that are in the RECAP collection, which accounts for several million additional opinions.
