MediaPost: Worldwide advertising spending will slow down in 2015 from previous estimates. U.K.-based Warc, the marketing researching service, projects advertising spending to now rise 2.3%, due to concerns in the U.S. and China markets. Internet ad spending will continue to make sharp gains — 16.1% and 12.9% this year and next. Warc said the Internet will become the largest medium for advertising in 2016. The Net is already the biggest ad platform in 6 of 12 major markets.