Financial advisors face difficult challenges given the global economic and financial crisis. Yet advisors can not only survive the downturn, but also thrive during it, according to the authors of a new book, Marketing for Financial Advisors: Build Your Business, Bring in Clients, and Establish Your Brand . According to Wharton marketing professors Eric T. Bradlow and Patti Williams , and Keith Niedermeier, director of Wharton’s undergraduate marketing program, the struggling economy provides an opportunity to “attack” and gain market share. Moreover, the industry has underinvested in marketing, they say, leaving low-hanging fruit to those who use the right tools. In an interview with Knowledge at Wharton, Bradlow, Williams and Niedermeier discuss how financial advisors can build their book of business — even in a down economy — by adopting data-driven and niche marketing principles.…