Poseidon is the god of the sea, Dionysus of wine and merrymaking, and Emily Oster? She’s the god of parenting.  An economics professor at Brown University, Oster has built a massive and loyal audience by providing overwhelmed parents with the information and data they need to make solid and sound parenting decisions in a very confusing world. Her first book, Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know, sold over a million copies and was translated into 19 languages, unseating the classic What to Expect When You’re Expecting as a fixture...