Securities firms around the world will cut as many as 80,000 jobs in the next 18 months as revenue growth begins to slow, said Meredith Whitney, the former Oppenheimer & Co. analyst who now runs her own firm. The reductions, about 10 percent of current levels, will come after 2010 compensation payments, Whitney, 40, said in a report dated Aug. 31 and obtained by Bloomberg News today. The industry’s payouts will be “down dramatically,” said Whitney, who started New York-based Meredith Whitney Group after correctly predicting Citigroup Inc.’s dividend cut in 2007. “The key product drivers of Wall Street’s revenues and profits over the past decade have been in a structural decline over the past three years,” Whitney said in the report. “2010 marks the first year in many in which Wall Street-centric firms will go through structural changes.”