A NY Times article on emerging patterns of migration shows that illegal immigrants are more likely to stay, in part because of better wages to be found farther from the border in the northeast, but more importantly, because security and vigilantism makes seasonal migration expensive and more dangerous.

Returning Mexicans, researchers say, have generally been divided between “sojourners,” those with temporary or seasonal jobs in the United States who cross once or more a year, and “settlers,” those who move to the United States for an extended period but at some point choose to return home.

“The Mexican migration was always round trip,” said Jorge Durand, director of the Mexican Migration Project at the University of Guadalajara, a research program in conjunction with the Office of Population Research at Princeton. “It was a migration of workers, not immigrants.”

But several factors are causing more illegal immigrants to stay in the United States. Increasingly, immigrants are finding jobs away from the agricultural sector, meaning they have more stable employment that is not subject to seasonal ups and downs, researchers say. More immigrants have also moved to destinations beyond the border states of the Southwest, making the journey back home longer, more expensive and less convenient.

Most important, some researchers say, increased vigilance along the border has led to higher costs and risks associated with crossing back into the United States, disrupting what had been the traditional circular movement of the migrants. Border enforcement began to tighten in the mid-1980s, but has become much more vigorous since the Sept. 11 attacks.

“Having run the gantlet of enforcement resources at the border, migrants grew reluctant to repeat the experience and hunkered down to stay, causing rates of return migration to fall sharply,” said Douglas S. Massey, a sociologist who directs the Mexican Migration Project at Princeton.

Demetrios Papademetriou, president of the Migration Policy Institute, a nonpartisan research group in Washington, said that “the primary effect of hardening the border has been one of locking people in.”