For that reason, OECD economist Jean-Christophe Dumont says the overall assessment is one of "stabilizing" migration. Dumont explains that it is too early to say whether there is a long-term downward trend in migration to Europe or North America.
"Overall, the migration flows towards the OECD countries [are] slowly stabilizing," Dumont says. "The total number that we have for European countries is 2.4 million in 2004. It was 2.6 million in 2002."
Detailed figures for 2004 are n-o-t yet available. But Dumont notes that migration to southern Europe remains "very dynamic" and that those numbers are "not decreasing yet." But he says the latest data show fewer foreigners are moving to other OECD countries.
"In the U.S. in 2003, the figure is about 700,000 entrants for permanent migration, where it was about 1 million the year before," he says. "So the decrease is quite sharp in the U.S. in 2003. This decrease is also observable in some other countries. For instance, in Canada it has been decreasing very slightly in recent years -- in Germany, for instance; the Netherlands, Norway, Sweden to a lesser extent; and obviously the decline in the U.K. for the first time after maybe 10 years of sharp increases in migration flows."
On 22 March, the OECD released its annual report on "Trends in International Migration." It explains that governments in many OECD countries have been imposing stricter laws about the entry and residence of foreigners in order to better manage migration flows.
Dumont says one obvious conclusion is that immigration to some countries is becoming more difficult due to tighter immigration laws passed after the September 11, 2001, terrorist attacks in the United States.
On 23 March, U.S. President George W. Bush said he remains concerned about the possibility of international terrorists moving into the United States. Bush says the issue of tighter border controls needs to be addressed together with the governments of neighboring Canada and Mexico.
"We've got a large border with Canada. We've got a large border with Mexico," Bush said. "There are [about 1] million people a day crossing the border from Mexico to the United States, which presents a common issue, and that is: How do we make sure those crossing the border are not terrorists or drug runners or gun runners or smugglers?"
But Dumont and other migration experts say there are other reasons besides security to explain the migration declines of 2003.
Sean Murray is the principle officer of the Irish government's Economic Migration Policy Unit. He tells RFE/RL that a weaker economic situation in the West is a likely factor.
"In 2003, things in the global economy weren't as buoyant as they are now or had been in 2004," Murray says. "That would be a natural correlation between migration flows and, indeed, economic growth. If economic opportunity doesn't exist, people would be more reluctant or less willing to move. There's little purpose in moving from one country to another if you are going to be unemployed in [your home] country and [also] be unemployed in another [country], where job opportunities are not as buoyant as they might have been formerly."
Ireland is one of the OECD countries that have introduced selective immigration policies to attract highly skilled workers. Others include Australia, Canada, and the United Kingdom. The OECD says those countries -- together with the United States, France, and Germany -- have gained the greatest number of highly skilled workers in recent years.
Murray says those who are thinking about migrating to the West in order to improve their economic situation should expect a very competitive job market.
"People may not get instantly a job commensurate with their experience or qualifications," he says. "A major factor in all of this is the language. We are urging people -- if they are planning to come here -- [they should] make sure they have sufficient proficiency in English to enable them to gain the type of job that their qualifications and experience would warrant."
Other striking comparative figures in the OECD report concern the number of students studying abroad.
Although the United States continues to host more foreign students than any other country, the OECD says the number of foreign students there has fallen from more than 300,000 in 2001 to about 210,000 in 2003.
Meanwhile, during that same period, the number of foreign students rose by 36 percent in the United Kingdom, by 30 percent in France, and by 13 percent in Australia.
Dumont says Australia now has the second-largest number of foreign students at its universities -- about 170,000.
"Some countries have been very active in trying to attract foreign students -- such as Canada, Australia, France, and the United Kingdom," Dumont says. "And in those countries, the increase in terms of inflow of foreign students has been quite impressive. At the same time, in the U.S. -- because of tougher measures to control and to manage migration, and to make sure that the system is in line with security measures -- the number of students going to the United States has been declining. By approximately 25 percent over the last three years. But the U.S. is still a magnet for foreign students, and they still accept a lot of foreign students. The U.S. is still the first."
Dumont also says the three-year declining trend for foreign students in the United States could come to an end when data for 2005 are compiled.
Foreign-student organizations have complained since late 2001 that security-clearance procedures have caused unpredictable delays for students trying to enter the United States. They say security requirements often have caused delays of months -- forcing many students to cancel their studies.
But a month ago, the U.S. State Department announced that lengthy procedures to obtain security clearances for science and engineering students will become shorter. Many of the foreign students in the United States pursue engineering and science degrees.