CREATE TABLE Research_Staff (employer_organisation_id VARCHAR(255)); CREATE TABLE Organisations (organisation_type VARCHAR(255), organisation_id VARCHAR(255))
Which organisation type hires most research staff?
    
SQL: SELECT T1.organisation_type FROM Organisations AS T1 JOIN Research_Staff AS T2 ON T1.organisation_id = T2.employer_organisation_id GROUP BY T1.organisation_type ORDER BY COUNT(*) DESC LIMIT 1