Hill: Unheralded and unnoticed, American oil producers are helping stabilize global oil prices, which would be a lot higher if new U.S. oil supply, mostly from shale, werent reaching world markets. Public attention usually focuses on shale from the perspective of local business benefit or environmental concern. Holding down prices doesnt figure as a benefit but its a story worth telling. Even with Saudi Arabia pumping oil at its fastest clip in decades, oil prices remain stubbornly high. For example,...