ET, oil-field services company Core Laboratories (NYSE: CLB) is down 5.2%, oil major Chevron (NYSE: CVX) is losing 4.8%, and further down the supply chain, refiner Phillips 66 (NYSE: PSX) is suffering worst of all with a 7.5% loss. What happened For the second day in a row, oil prices are tumbling Thursday -- and they're taking down shares of companies all across the energy industry along with them. For example, this morning The Wall Street Journal reported that gasoline prices near $5 per gallon nationally have begun to depress consumer demand.