No one can say how many are leaving. But in the last half year, the reverse migration has become unmistakable among Brazilians in the United States, a population estimated at 1.1 million by Brazil’s government — four to five times the official census figures.

To explain an often wrenching decision to pull up stakes, homeward-bound Brazilians point to a rising fear of deportation and a slumping American economy. Many cite the expiration of driver’s licenses that can no longer be renewed under tougher rules, coupled with the steep drop in the value of the dollar against the currency of Brazil, where the economy has improved.

“You put it all together, and why should you stay in an environment like that if you have a place like Brazil, where there’s hope, a light at the end of the tunnel and it’s not a train to run you over?” said Pedro Coelho, a businessman in Mount Vernon, N.Y., who is known as the mayor of Brazilians in Westchester County. “Are they leaving? Yes, by the hundreds.”

In Massachusetts, says Fausto da Rocha, the founder of the Boston-area Brazilian Immigrant Center, his compatriots — many here illegally — are leaving by the thousands, some after losing homes in the subprime mortgage crisis. In New York and New Jersey, travel agents and others who sell airline seats say that one-way bookings to Brazil have more than doubled since last year, to about 150 daily from Kennedy International Airport, and that flights are sold out through February.

And at Brazil’s consulate in Miami, which serves Brazilians in five Southeastern states, officials said a recent survey of moving companies and travel agencies confirmed what they had already surmised from their foot traffic: More Brazilians are leaving the region than arriving — the reversal of an upward curve that seemed unstoppable as recently as 2005, when Brazilians unable to meet tightened visa requirements were sneaking across the United States-Mexico border in record numbers.