Mark Penn made his name as a numbers guy, using his legendarily detailed polling to re-elect Bill Clinton and keep him remarkably popular in the face of repeated scandal. Very few, however, have ever really seen the numbers that led to his reputation as a bit of a PR magician. So consider Penn’s new book, Microtrends: The Small Forces Behind Tomorrow’s Big Changes, written with E. Kinney Zalesne, as a bit of a magic show. Penn, of course, is famous as the guy who invented the term “soccer moms” and hence introduced the not-so-micro trend of atomizing the American electorate into oblivion. Any time you hear a pundit refer to “NASCAR dads” or “security moms,” it’s at least partly Penn’s fault. The book details 75 groups that supposedly prove Penn’s adage that “small is big.” Some of Penn’s categories are pretty familiar: “cougars,” “social geeks,” and, yes, “car-buying soccer moms.” Others, it’s just hard to think of as trends: “30-winkers” (those who get fewer than 40 hours of sleep a week) or “snowed-under slobs,” for instance—didn’t we used to just call these people “insomniacs” and “pack rats?” Penn discusses and signs copies of his work at 6 p.m. at Politics and Prose, 5015 Connecticut Ave. NW. Free. (202) 364-1919.