Forecasts for third-quarter S&P 500 earnings now call for a 3.9 percent decline from a year ago, based on Thomson Reuters data, with half of the S&P sectors estimated to post lower profits thanks to falling oil prices, a strong U.S. dollar and weak global demand. A rolling 12-month forward earnings per share forecast now stands near negative 2 percent, the lowest since late 2009, when it was down 10.1 percent, according to Thomson Reuters I/B/E/S data.