Unilever CEO Paul Polman is one of the most prominent advocates of companies pursuing an agenda of sustainability and this week he outlined the company's progress. Meanwhile, Wal-Mart Stores was forced to react to claims of bribery in its Mexican operations and Nestle's acquisition of Pfizer's baby food business was scrutinised by analysts. The investment community also had a raft of first-quarter results to get their teeth into, with Kellogg, PepsiCo, Premier Foods plc and Hershey among the companies reporting.