Sales of illegal antiquities total at least $7.8 billion annually. It’s a black market that ranks behind only drugs and weapons as the most profitable, according to a United Nations analysis.

What comes out of the ground passes through international networks of plunder. At the end of the line, people purchase archaeological artifacts in shops, on the Internet and in private and public auctions. Buyers rarely know or, apparently, care how a $2.99 Native American arrowhead or a $75,000 Egyptian sarcophagus managed to come into their possession.

During the Archaeological Institute of America’s annual meeting, held in Philadelphia in January, researchers offered analyses of auction and Internet data documenting an ongoing demand for archaeological artifacts. Buyers show no hesitation when offered desirable items that have no documented ownership history, or provenance. Auction-house catalogs of available items contain a fair number of fake pieces and genuine ones illegally obtained.

The laws and conventions aimed at stopping illegal looting are difficult to enforce.