Mexican drug traffickers supply 75 percent of all cocaine shipments to the United States, 30-50 percent of the heroin, and over 90 percent of the methamphetamine consumed each year by U.S. drug abusers. Cartel leaders have paid hundreds of millions of dollars in bribes to hundreds of Mexican police and other government officials to buy protection, information, and assistance in entering the United States illegally. Also, drug traffickers in Mexico have contracted with police officials to murder other officials, guard drug shipments, and warn suspects about investigations, including providing the names of witnesses who might testify against them. A shift in U.S. drug strategy under the Clinton Administration killed or reduced U.S. funding for sophisticated equipment used by Mexicans in destroying marijuana and opium poppy fields. From 1992 to 1996, U.S. funding for interdiction in the Transit Zone was cut nearly in half. The Clinton Administration reversed course in 1996 with the appointment of Barry McCaffrey as head of the White House Office on National Drug Control Policy; spending was increased for drug interdiction operations on the U.S.-Mexico border and in the Caribbean region. Drug-related corruption in Mexico is likely to increase, however, until there is a significant change in Mexicans' cultural attitudes about corruption. Recent years have seen a decrease in public tolerance for corruption, but decades may pass before any significant change in drug-related public corruption occurs.