When policy makers in Washington worry about Mexico these days, they think in terms of a handful of numbers: Mexico's 19,500 hectares devoted to poppy cultivation for heroin; its 17,500 hectares growing cannabis; the 95 percent of American cocaine imports brought by Mexican cartels through Mexico and Central America.

They are thinking about the wrong numbers. If there is one number that embodies the seemingly intractable challenge imposed by the illegal drug trade on the relationship between the United States and Mexico, it is $177.26. That is the retail price, according to Drug Enforcement Administration data, of one gram of pure cocaine from your typical local pusher. That is 74 percent cheaper than it was 30 years ago.

This number contains pretty much all you need to evaluate the Mexican and American governments' "war" to eradicate illegal drugs from the streets of the United States. They would do well to heed its message. What it says is that the struggle on which they have spent billions of dollars and lost tens of thousands of lives over the last four decades has failed.

There is little reason to expect the elections this year will do much to address the challenges to the bilateral relationship. Enrique Peña Nieto, elected president of Mexico on Sunday, is a scion of Mexico's Institutional Revolutionary Party, which was tainted by authoritarianism, corruption and fraud during seven decades in power, before it was booted out by voters 12 years ago. In the United States, neither President Obama nor his Republican challenger, Mitt Romney, has shown much interest in the nation's southern neighbor.

Yet the presidential elections on both sides of the border offer a unique opportunity to re-examine the central flaws of the two countries' strategy against illegal narcotics. Its threadbare victories - a drug seizure here, a captured kingpin there - pale against its cost in blood and treasure. And its collateral damage, measured in terms of social harm, has become too intense to ignore.

Most important, conceived to eradicate the illegal drug market, the war on drugs cannot be won. Once they understand this, the Mexican and American governments may consider refocusing their strategies to take aim at what really matters: the health and security of their citizens, communities and nations.

Prices match supply with demand. If the supply of an illicit drug were to fall, say because the Drug Enforcement Administration stopped it from reaching the nation's shores, we should expect its price to go up.

That is not what happened with cocaine. Despite billions spent on measures from spraying coca fields high in the Andes to jailing local dealers in Miami or Washington, a gram of cocaine cost about 16 percent less last year than it did in 2001. The drop is similar for heroin and methamphetamine. The only drug that has not experienced a significant fall in price is marijuana.

And it's not as if we've lost our taste for the stuff, either. About 40 percent of high school seniors admit to having taken some illegal drug in the last year - up from 30 percent two decades ago, according to the Monitoring the Future survey, financed by the National Institute on Drug Abuse.

The use of hard drugs, meanwhile, has remained roughly stable over the last two decades, rising by a few percentage points in the 1990s and declining by a few percentage points over the last decade, with consumption patterns moving from one drug to another according to fashion and ease of purchase.

For instance, 2.9 percent of high school seniors admit to having tried cocaine in the last year, just slightly less than in 1992. About 15 percent of seniors said they abused a prescription drug last year. Twenty years ago, prescription drug abuse was not even consistently measured.

The only dimension along which the war on drugs might be conceived as a success is political. If you ask Americans how concerned they are about drugs, they will give you roughly the same answer they have given for years: not so much.

In a Gallup poll, only 31 percent of Americans said they thought the government was making much progress dealing with illegal drugs, the lowest share since 1997. But fewer people say they worry about drug abuse than 10 years ago. Only 29 percent of Americans think it is an extremely or very serious problem where they live, the lowest share in the last decade.

But the government has spent $20 billion to $25 billion a year on counternarcotics efforts over the last decade. That is a pretty high price tag for political cover, to stop drugs from becoming a prominent issue on voters' radar screen. It becomes unacceptably high if you add in the real costs of the drug wars. That includes more than 55,000 Mexicans and tens of thousands of Central Americans killed by drug-fueled violence since Mexico's departing president, Felipe Calderón, declared war six years ago against the traffickers ferrying drugs across the border.

And the domestic costs are enormous, too. Almost one in five inmates in state prisons and half of those in federal prisons are serving time for drug offenses. In 2010, 1.64 million people were arrested for drug violations. Four out of five arrests were for possession. Nearly half were for possession of often-tiny amounts of marijuana.