After oil prices plummeted, I went on the record saying I thought they'd be back above $70 per barrel by the end of 2015. The year isn't over yet, but my prediction isn't looking good. I thought worldwide demand would go up — and it has. The latest from the International Energy Agency shows demand is already up about 1.7 million barrels a day. thought supply from the United States would go down — and it has. Companies have been laying down rigs, and U.S. production has dropped by 500,000 barrels a day since June. So where'd I go wrong?...