What happens when Saudi Arabia, the world's swing producer of oil, rejects its traditional market-balancing role? The job falls to American shale oil producers, which, initial data show, appear to be assuming the Saudi role. Using data collected by the Austin energy analytics firm Drillinginfo, Baker Institute energy fellow Jim Krane and energy studies graduate fellow Mark Agerton write that some shale producers are cutting back on drilling and new production in response to plummeting oil prices.