The thinking behind an intelligence assessment for Iran's damaged nuclear program

A leaked US Defense Intelligence Agency's assessment said the damage to Iran's nuclear program from American bombing pushed the program back by months. An Israeli intelligence assessment claimed it pushed it back years. The Trump administration insists it was "obliterated." The World's Host Marco Werman talks with Jeffrey Lewis, a professor at the James Martin Center for Nonproliferation Studies at the Middlebury Institute of International Studies at Monterey, about the methods intelligence agencies use to determine what's going on.