Speculators increased bullish oil bets by the most in more than four years, wagering that the U.S. production boom is slowing. Hedge funds boosted net-long positions on West Texas Intermediate crude by 30 percent in the seven days ended April 7, the biggest jump since October 2010, U.S. Commodity Futures Trading Commission data show. U.S. crude output and inventories may peak this month amid a record drop in rigs exploring for oil, Goldman Sachs Group said.