THE DEMAND SIDE. As the immigration debate lurches forward, lots of folks have asked why there's so little focus on the demand side. Wouldn't it be easier to dry up the jobs than patrol the desert? My read is that you couldn't totally staunch the flow by patrolling employers, but you could sure put a dent in it, and today's comprehensive Los Angeles Times article tells you some of the reasons why:

� One fairly sure indicator of the existence of illegal aliens on a worksite is Social Security tax payments for large numbers of workers that do not match any known taxpayers. The only problem is the immigration authorities have no access to the Social Security Administration's records; they're not given the names of offending companies or of suspicious workers.

� The number of federal workers charged with finding illegals on the job has plummeted, from 240 in 1999 to 90 in 2003.

� Only one percent of the funds devoted to immigration enforcement is directed to workplace operations. Last year a mere 127 employers were convicted for hiring undocumented workers. Calling that a drop in the bucket vastly overstates its reach and effectiveness.

� Hiring undocumented workers became illegal in 1986. The enforcement method is the I-9 form, which states that workers are citizens, permanent residents, or authorized workers, with identification. Employers can use any of 29 different documents for ID, including report cards for those under 18. There is no way to sift genuine documents from forgeries, and with so many potential types of documents in play, catching fakes is near impossible. Employers, knowing this, often hire aliens with full knowledge of their status and total assurance, thanks to a half decent forgery provided by the immigrant, of their own plausible deniability.

� There's a fairly simple program called Basic Pilot that could fix much of this. BP forces employers to enter employee information into the database within three days of hiring. The info is then checked against SSA and DHS data, and if the numbers don't fly, the employee must be fired. The problem is, not all of BP's computers are linked, and it tends to encourage identity theft, with multiple folks using the same name and social security number. And, in any case, the authorities in charge of Basic Pilot won't share the data with immigration enforcers for fear that fewer employers will use it.

� Employer sanctions have plummeted: in 1999, 417 employers were fined for knowingly hiring an undocumented immigrant. In 2004, it was three.

Of course, Republicans, excited to demonize poor immigrants, aren't nearly so enthusiastic about taking on business. So even if some of this were fixed, nothing onerous, which is to say effective, would result. Illegal immigration is a potent political issue because the folks being screamed at are scared to even whisper back. Turning your fury on the corporate community -- even if it's more justified -- results in a far fairer fight, and that's the last thing a demagogue wants.

--Ezra Klein