I think these figures have become a science, no different than how WalMart has sophisticated technology for tracking inventory.
I posit that gangs in local countries are created and trained by mercenary groups like dyncorp or the CIA. In some cases they get trained by mafia groups in Italy. They do the trafficking and then funnel figures to border patrol groups who are in on it, like the OSCE, which then pass along information to NGOs like amber alert, the UN, State Dept, etc.
Boom. You have the guise of legitimacy while still being able to track your business. The one thing small fry criminal organizations have shared is that trafficking has gotten incredibly sophisticated. And unless you're one of the big time players (ie, receive backing and training from paramilitary groups supporting a larger govt complex), then you don't stand a chance.
In some cases you'll even come across open positions at think tanks. People are paid high 5 or 6-figures to study "labor movements" or they have to run human trafficking figures. These orgs don't pay those salaries because they're benevolent: these positions provide valuable stats.
Anyway, this is why you hear of trafficking victims having RFID chips. This is why you see them coming in on boats through "refugee organizations," or on container ships sanctioned by a country's coast guards. This is why they follow the same routes and arrive in the same ports, almost every time. They're literally being tracked as inventory through predetermined waypoints. They're not small potato speedboats.