Stocks worldwide plunged Tuesday after Chinese markets fell 9 percent - their biggest drop in a decade. Jim Lehrer looks at why the stock market had such a bad day. Gwen Ifill reports on the latest developments on Iraq, both on the ground and in Washington. Judy Woodruff reports on the cervical cancer vaccine for young girls. The guests this episode are Susan Dentzer, Ralph Anderson, Wendy Wright, Marcia Coyle, Nuruddin Farah. Byline: Jim Lehrer, Gwen Ifill, Judy Woodruff, Ray Suarez, Jeffrey Brown