1. Experience (in years) in the labor market / staff. Yes, indeed, experience is a key advantage in recruiting, as well as in law, medicine and psychology. All intellectual services: the more experienced doctor, lawyer or teacher, the higher its professionalism, the greater the probability of obtaining the desired result. Typically, recruitment Agencies serious enough experience is acquired through 3-4 years of work.
Also, you should distinguish between the work experience of the agency itself, as the TM and the experience of its staff as the main resource. Both indicators are important. Experience can be measure (and even check!) on the list of previous clients, according to the so-called "Client-list" of authorized documents, reviewing the chronology of events on the agency website. Or even simpler: if the agency its "longevity" is as advantage, ask his staff to prove their own documented approval. 2. Volume database of job seekers. A large database – this is how much? 10000 – this is much or little? And which agency will allow you to it check? Do a large database to search for unique specialist or even a chef, if in only 10-15 decent restaurants and, accordingly, such experts? Nevertheless, a large database allows agency to expand the search area and thus increase the "hit accuracy." On the other hand, a large volume of resumes in the bank allows the agency to close many vacancies "on the spot", ie from the computer without waiting for the impact of advertisements and other sources of search.