Depending on what you consider what a cartel member is. Take Los Zetas for example, in each town or small city the Los Zetas have about 50-80 cartel soldiers but for each soldier they have about 4-10 criminals that work for them;some are hired guns, others are lookout or retail drug dealers and others all are a combo of a little bit of everything. There is a good Insight Crime Anaylisis article about Los Zetas that clears it up a bit more than me.

Take a read on the second post of the Insight Crime Analysis of Los Zeta thread. It really goes into about their economic model, membership status, and how they operate as a organization. http://www.gangsterbb.net/threads/ubbthreads.php?ubb=showflat&Number=686503#Post686503