Thalia's classmate, Sarye, says her mother was willing to face the dangers of a desert crossing because she was tired of working 12-hour days at a restaurant in Mexico City.

NPR: Immigrant Students Talk About U.S. Life

In a deliberately provocative speech, David Cameron, the Tory leader, adopted the metaphor of a caravan crossing the desert to highlight the importance of making sure that the income growth of the poorest keeps pace with the rest.

ECONOMIST: Income inequality

In 2005, for instance, he dismissed a lawsuit against the U.S. Department of the Interior by the families of 11 illegal immigrants who died crossing the Arizona desert.

WSJ: Family, Colleagues Grieve for Slain Judge, John Roll

He says he could then safely travel back and forth instead of risking his life crossing illegally through the desert and spending thousands of dollars for an immigrant smuggler.

NPR: Kennedy, McCain Introduce Immigration, Guest Worker Bill

As he speaks, stunning images of the Golden Gate bridge and Santa Monica's palm trees clash with a cow crossing a freeway in a drab Nevada desert.

ECONOMIST: Emigration from California

The challenging route has desert stages virtually from the outset, then goes through gaucho territory in Argentina after crossing the Andes before the challenge of the Chilean dunes.

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