The latest exits were the result of studies the bank began in early 2012 to figure out which countries were not profitable enough for retail banking. A spokesman for Citigroup said the bank has long had systems in place to consistently measure profitability across businesses and geography. The deliberate pace at which Chief Executive Officer Michael Corbat is fixing its business underscores how hard it is to fix a business as sprawling as Citigroup, which operates in more than 100 countries.