The Mexican border functions as a drum that both the left and the right like to thump. For the left, it means imperialism. They decry the death of migrants, the newly built wall and the tens of thousands of armed agents patrolling the line. The right sees the border as the only thing separating us from the disintegration of our national security. They decry migrants (illegal invaders), violence spilling over the border and, in certain zany moments, see Islamic terrorists crossing the desert and leaving a litter of prayer rugs.

The migration of the Mexican poor is the largest human movement across a border on the planet. It was triggered by the destruction of peasant agriculture at the hands of the North American Free Trade Agreement, by the corruption of the Mexican state, by the growing violence in Mexico, and exacerbated by the millions of Mexicans working illegally in the U.S. who send money home to finance their families' trips north. It should be seen as a natural shift of a species. We need ecologists on the border; the politicians have become pointless.

The drug industry is the second-largest source of foreign currency in Mexico, just behind oil. It earns somewhere between $30 billion and $50 billion a year -- no one really knows, including the people in the industry. It also creates enormous numbers of jobs in the U.S.: We spend billions a year on narcs, maintain the world's largest prison industry, which is absolutely dependent on the intake of drug felons, and we have about 20,000 agents on the border who feed off drug importation. The rehab industry is also a source of a large number of jobs since many well-heeled defendants pick mandatory treatment over prison. Many county and local police departments now get fat off of RICO suits based on drug offenses.

The official line of the U.S. government, one most recently voiced by Secretary of State Hillary Clinton, is that drug consumers in the United States are responsible for drug murders in Mexico. Only someone who is drugged could believe this claim. The sole source of the enormous amount of money in the drug business and the accompanying violence is the U.S. prohibition of drug use by its citizens. Since President Richard Nixon proclaimed the War on Drugs 40 years ago, there have been two notable accomplishments: Drugs are cheaper than ever, and they are of much higher quality. But then, NAFTA was promoted by presidents George H.W. Bush and Bill Clinton as something that would buoy up the Mexican economy and reduce or end illegal immigration -- two claims that now are clearly refuted by facts.

The left seeks open borders or No More Deaths, the latter a protest of the 500 or so migrant deaths per year -- a rather low fatality rate, considering that at least a half-million Mexicans move illegally across the border each year. But the left seldom if ever mentions the slaughter in Mexico during the last three years that has left 17,000 citizens dead, a killing of Mexicans by Mexicans. The right constantly speaks of fortifying the border, as if this could stop a human tide lashed northward by misery. And, of course, the right promotes draconian drug laws even though the failure of such laws is increasingly apparent.

On the border, Adam Smith meets magical realism. Here the market tenets of supply and demand, the basic engine of both the migration and the drug industry, are supposed to be overturned magically by a police state. Consider one simple number: The border is 1,900 miles long. If two people slipped through each mile in a 24-hour period, that would amount to 3,800 people a day. That adds up to 1,387,000 people a year. Or consider this: One bridge from Juarez to El Paso handles 600,000 semi-trucks a year. One semi with a freight load of 24 tons could probably tote enough heroin to satisfy the U.S. market for a year. Add to the mix the inevitable corruption of the police agencies: A few months ago, a Border Patrol agent in southern Arizona was busted for running dope in his official car for 500 bucks a load.

Few discussions about the border come from facts. Most discussions of the border come from fears. We seem to prefer slogans and fantasies: free trade, "just say no," gigantic walls.