President Obama says his proposals to crack down on corporate tax loopholes will do a lot of things, including create more U.S. jobs. "We will stop letting American companies that create jobs overseas take deductions on their expenses when they do not pay any American taxes on their profits," Obama said when announcing his proposals. In turn, Obama said, the government would offer a tax cut to companies that do their research and development in the United States. And that will "jump-start job creation," he said. Will it work? Tax policy experts and corporate lobbyists are dubious. They say that...