Illegal firearms markets: Transaction patterns, evolving sources, and importance in criminal misuse.

In the United States, the legal status of the 30 to 40 million annual firearms transactions is defined by state and federal regulations. These regulations primarily aim to reduce criminal misuse while preserving access for the large majority of adults who lack a serious criminal record or are otherwise proscribed from possession. Illegal firearms transactions are embedded in the "formal market"-sales, mostly of new guns, by licensed retail dealers required to screen purchasers and maintain records-and the "informal market," where any of the 80 million gun owners may act as a source. A growing fraction of illegal transactions involve privately made firearms, fabricated from commercial kits or additive manufacturing techniques. The firearms used by proscribed people are diverted from the legal supply chain, in some cases by professional intermediaries (thieves, straw purchasers, scofflaw dealers, home fabricators). Subsequent redistribution may involve professional brokers and traffickers. Most such enterprises are small in scale, with organized criminal groups serving primarily as customers rather than distributors. Compared with the drug trade, the illegal gun market is smaller and more exposed to law enforcement. For proscribed buyers, transaction costs are highly differentiated, varying based on the local prevalence of guns, state regulations and enforcement, and individual connections. While preventing dangerous people from obtaining guns is intrinsically difficult in a regime designed for broad accessibility to most adults, regulations can substantially affect illegal commerce, and some regulations reduce criminal use.