Fewer Americans are drinking Coke, as the once dominant drink loses ground to bottled water, coffee, and energy drinks. Sales of cocaine, originally a key ingredient in Coca-Cola KO, -0.19% , are experiencing a similar decline.

These days, users of illegal drugs in the U.S. have more in common with the pot-smoking slackers from “Harold and Kumar Go to White Castle” than the cocaine-snorting villain Patrick Bateman from “American Psycho.”

Although the individual patterns of heroin, cocaine, marijuana and crystal meth abuse have changed dramatically over the past decade, Americans still spend more than $100 billion a year on these drugs, a figure that has changed little during the past several years. The use of cocaine across the U.S. halved from 2006 to 2010, while the amount of illegal marijuana bought increased by nearly one-third over the same period, according to a new report, “What America’s Users Spend on Illegal Drugs, 2000-2010,” by the White House Office of National Drug Control Policy.

People spent more than 1 trillion dollars on cocaine, heroin, marijuana and methamphetamine between 2000 and 2010, says Beau Kilmer, co-director of the RAND Drug Policy Research Center in Santa Monica, Calif. Cocaine and marijuana had opposite trajectories over that period. There was $55 billion spent on cocaine in 2000 versus $28 billion in 2010, but marijuana use rose from $22 billion to $41 billion over the same period. Heroin spending rose from $23 billion in 2000 to $27 billion in 2010, while methamphetamine spending rose from $8 billion to $13 billion.

Law-abiding Americans who’ve never touched an illegal drug in their lives should be concerned, Kilmer says. U.S. taxpayers end up picking up the bill, paying approximately $200 billion a year — or double the $100 billion drug users themselves spend annually on illicit drugs — for police, health, crime and incarceration costs associated with illegal drug activity, Kilmer adds. On the upside, there tends to be less violent crime associated with marijuana distribution than with harder drugs like crack cocaine, he says. “There are serious social costs associated with heavy cocaine use, so a reduction is good news,” Kilmer says.

So why the drop in cocaine use? “This is mostly due to interruption of cocaine shipments to the U.S.,” says Daniel Mejía, director of the research center on drugs and security at University of the Andes, Colombia. Authorities in Colombia — where 80% to 90% of the U.S. cocaine market comes from — have cracked down on cocaine production, shutting down laboratories and imprisoning drug lords. Net cocaine production — potential cocaine production minus seizures — there has plummeted to 189 metric tons in 2011 from 605 metric tons in 2000, Mejía says. As supply dropped in the U.S., prices rose from $115 per gram in 2000 to $169 per gram in 2011.

Availability issues aside, others say this points to the fact that marijuana may not be a gateway to harder drugs. “These figures belie that notion that marijuana exposure is an alleged gateway to the use of other illicit substances,” says Paul Armentano, deputy director of Norml, the national organization for the reform of marijuana laws. Over 75% of people who use marijuana recreationally do so as a substitute for at least one other substance, including cocaine and alcohol, according to one 2012 report published in the journal Addiction Research and Theory.

Opinion: The Philip Morris of Marijuana?

Those trends have continued in recent years. In 2012, there were 24 million people ages 12 and over, more than 9% of the population, using illicit drugs, according to the Substance Abuse and Mental Health Services Administration, or Samhsa. That includes hallucinogens and prescription psychotherapeutics (pain relievers, tranquilizers) for non-medical use. Marijuana was the most common, rising from 5.8% to 7.3% between 2007 and 2012, or from 14.5 million to 18.9 million people. In 2012, 1.6 million people or just 0.6% of the population used cocaine, versus 2.4 million or 1% of the population in 2003.

Of course, heroin remains a serious problem in certain states, particularly Vermont; the U.S. Senate Judiciary Committee this week held a hearing into the growing heroin problem in that state. And the use of methamphetamine — also known as crystal meth — in the U.S. dramatically increased during the first half of the decade and subsequently declined, Kilmer says. Some 440,000 people or 0.2% of Americans ages 12 and over used meth in 2012, a drop from 2006, when it hovered at 730,000 or 0.3%, according to Samhsa. (Also see: “How Breaking Bad is bad for meth dealers.”)

Other articles by Quentin Fottrell:

How to invest in legalized marijuana

Treating hangovers is now a billion-dollar industry

Is America facing a beer crisis?

What’s behind the return of the 1980s cellphone