U.S. shale producers are telling investors impatient for better returns that they can keep boosting oil output aggressively and do so while still making money for shareholders.  Investors have pushed top U.S. shale companies to focus on returns, rather than higher output, a move that threatened to slow the breakneck growth in supply sparked by the shale revolution in the world’s top oil consumer. For the Organization of the Petroleum Exporting Countries, slower shale production gains would have been welcome. The cartel this year put caps on its members’ production to end a supply glut and boost oil prices, only to find U.S. shale gains and record exports muting the impact of their curbs. But in comments during recent third-quarter earnings […]