Twenty-four countries where oil production is in decline were identified. A simple metric of the volatility of oil production on the upslope of their production curves, called decline as a proportion of pre-peak production (or PPPmax), was created. PPPmax was determined for the post-peak countries and plotted as a frequency distribution. PPPmax varied from 0-56%, but was skewed toward the lower part of the range (median 6.24 As global production is determined by the total contribution of production from all countries, the variation in PPPmax will represent the lower and upper bound of the "bumpiness" of global oil production. It also enables a retrospective approximation of the when global oil production is most likely past its peak. (c) 2015 Elsevier Ltd. All rights reserved.