Opponents of illegal immigration have cause for celebration: data from law-enforcement agencies show that the number of people trying to enter the United States without documents by crossing the border with Mexico has fallen sharply.

This year the number of Latinos (mostly Mexicans) arrested and deported to their countries of origin has fallen to levels in the 1970s, when the undocumented stream had yet to become a full-flowing river.

The U.S. Border Patrol bases its evaluation of undocumented border crossings on arrest statistics. Although this method is not perfect, experts at the Congressional Research Service find it to be relatively reliable. The word “relatively” is appropriate since it is impossible to know exactly how many undocumented immigrants make it into the United States without running into border patrol agents.

Whatever the case, in the 2008 fiscal year ending September 30, border patrol agents arrested 705,000 people (almost 2,000 undocumented immigrants every day) trying to cross the U.S.-Mexican border. This is the lowest these numbers have been since 1976.

Both the U.S. Border Patrol and the Department of Homeland Security (DHS) led by Michael Chertoff explain their success as the result of stiffer measures taken in regard to undocumented immigrants, primarily the erection of a 1,934-mile fence along the border. The iron barrier already covers 70 percent of a 693 mile segment of California, Arizona and New Mexico. According to Chertoff, 525 miles of barriers have been erected since 2007. Work will continue next year with the beginning of construction in Texas.

In addition to the man-made obstacle, border patrol agents have also become barriers standing in the way of undocumented immigrants. In 1993 there were a total of 4,000 agents, while today there are already over 18,000 agents. Some of those detained are indicted as a warning to those planning on sneaking into the United States.

At the same time, Chertoff has admitted that the economic crisis has been another cause of the reduced flow of undocumented immigrants. But the Secretary of Homeland Security seems to think this cause is secondary and counts law enforcement actions as the primary cause. In my opinion, it is the high level of unemployment in the United States that has made our country less appealing in the eyes of illegal immigrants, not the arrests or the fences, which are very easy to get over in some places.

A Wall Street Journal article entitled “American Workers Crowding out Immigrant Laborers” draws attention to facts that were until recently difficult to imagine. “For the first time in a decade, undocumented immigrants are meeting with real competition for low-paying jobs from Americans,” writes the Journal. “Tens of thousands of them have lost their jobs since employers are able to fill vacancies with US citizens. Some undocumented immigrants have made the decision to forgo the competition and return home.”

According to the Pew Hispanic Center, in the third quarter of this year, 71.3 percent of Spanish-speaking immigrants were working or actively seeking work, compared with 72.4 percent in the same quarter of 2007. It would seem that a difference of 1.1 percentage points is not all that meaningful. However, the economist Rakesh Kochhar, who prepared the Pew report, believes that this figure is a very serious indicator of a significant drop in the number of Spanish-speaking immigrants (both legal and undocumented) in the labor market.

The Wall Street Journal gives the situation at the Los Angeles-based Hollywood Community Job Center as an example. According to the coordinator Rene Jemio, only Spanish was heard here until recently. Now many African-Americans and whites come to the center prepared to take on any job, even low-paying ones. There are, however, significant problems with work. One year ago contractors and homeowners visiting this unique employment agency offered work to 40 people a day, but now only about four people a day receive work.

And this is the situation not only in Los Angeles, but also in New York, Houston, and other cities with large immigrant populations. The recession in the construction industry, which used to employ between 20 and 30 percent of Spanish-speaking residents in the United States has dealt a significant blow to undocumented immigrants.

The depth of the American economic crisis can be judged by the current situation in the agricultural sector. American farmers once suffered from a constant shortage of workers and part of the harvest was simply lost in the fields. The situation has now shifted 180 degrees: the supply of free hands exceeds the demand for them. “This is the first time since 9/11 that we have not had problems with workers,” said Bob Gray, head of Duda Farm Fresh Foods. “We have enough U.S.-born people who are crowding out immigrants.”

All this means that hundreds of thousands of immigrants have been forced to return home because they had no livelihood.

Regardless of how deep the economic crisis gets, it will, of course, end sooner or later. Everything will return to normal in the agriculture and construction sectors: it is unlikely that either white or black Americans will last for long in these sectors. But the fact is that many undocumented immigrants who came to the United States to make money currently have nothing to do here.

“I am always hearing talk of emigration in the opposite direction,” said Jemio. “There is no point in staying in the United States without work.”