The Organization of the Petroleum Exporting Countries on Thursday left its forecast for growth in world oil demand this year unchanged at 2.3 million barrels a day, or mb/d, for an average of 101.9 mb/d. In its monthly report, the cartel warned the outlook “is subject to many uncertainties, including the trend and pace of economic activity in both OECD and non-OECD countries.” The Organization for Economic Cooperation and Development is made up of wealthy countries. OPEC said its forecast for demand growth across OECD countries was revised down for all four quarters, but lifted for non-OECD countries, boosted in part…