MediaPost: Carat, part of the Dentsu Aegis Network, has downgraded its global ad spend forecast for 2015. In a just-issued forecast revision, the agency is predicting 4% growth for this year to $529 billion. Earlier this year the agency had forecast 4.6% growth. Next year spending is expected to grow by another $25 billion (+4.7%). The downgrade was attributed in part to economic volatility in China and Russia, as well as by lower-than-anticipated growth in radio and outdoor.