From Suzanne Gamboa of the Associated Press comes this:

The online tool E-Verify, now used voluntarily by employers, wrongly clears illegal workers about 54 percent of the time, according to Westat, a research company that evaluated the system for the Homeland Security Department. E-Verify missed so many illegal workers mainly because it can't detect identity fraud, Westat said.

"Clearly it means it's not doing it's No. 1 job well enough," said Mark Rosenblum, a researcher at the Migration Policy Institute, a nonpartisan, Washington think tank...

...E-Verify correctly identified legal workers 93 percent of the time, Westat said. However, previous studies have not quantified how many immigrants were fooling the E-Verify system. Much of the criticism of E-Verify has focused on whether U.S. citizens and legal immigrants with permission to work were falsely flagged as illegal workers.

Sen. Chuck Schumer of New York, who is writing the Democrats' immigration bill and has fought expanding E-Verify because of its flaws, said Wednesday that the fact that E-Verify was inaccurate so often shows that it is not an adequate tool.

1. No doubt additional checks could be built into the system to increase its accuracy.

2. The MPI is only "non-partisan" in the New York Times sense.

3. The reasons why Schumer opposes expanding the system probably go a bit beyond just concerns about its flaws; he's never shown much interest in immigration enforcement.