Number of open pull requests
Might be more telling than total pull requests
SELECT count(distinct pull_request_id) as num_still_open, projects.name as project_name, projects.url as url
FROM msr14.pull_request_history
join pull_requests on pull_request_history.pull_request_id = pull_requests.id
join projects on pull_requests.base_repo_id = projects.id
where pull_request_id not in
(SELECT pull_request_id
FROM msr14.pull_request_history
where action = 'closed')
group by projects.id