London—Global ad spending will reach $489.0 billion this year, up 4.8% over last year, according to a new forecast from ZenithOptimedia. The forecast is up very slightly from a December projection of 4.7% growth for the year. Next year, global ad spending is projected to increase by 5.3%, up from an earlier projection of 5.2% growth, and in 2014, ad spending is expected to increase by 6.1%, up from an earlier forecast of 5.8%. ZenithOptimedia also revised its forecast for U.S. ad spending, which is projected to grow 3.6% this year (up from an earlier forecast of 3.5%). The fastest-growing media categories in the U.S. this year will be Internet ad spending (up 17.8%) and cable TV (up 10.0%), according to the report.