The U.S. Drug Enforcement Administration (DEA) keeps frequently updated price lists and tracks purity levels of a wide variety of illicit drugs, which federal, state and local law-enforcement agencies can use to put a value on drug seizures, Slate reported May 24.

The DEA's quarterly Trends in Trafficking report  -- not readily available to the public -- includes information compiled by the agency's 21 field offices. (Some of the data is included in a 2004 report from the Office of National Drug Control Policy.) Both wholesale and retail prices are reported based on information from informants and undercover agents. The DEA's report also includes information on drug purity based on testing of drug samples.

Typically, estimates of the price of seized drugs given to the public are based on wholesale prices in the market where the drugs were destined for sale. The report shows that both price and purity can vary significantly from region to region.

The DEA's price and purity data are considered the most comprehensive such information available.