The economically destructive price spike of 2007-2008 occurred when spare production capacity fell below 1 mbpd, causing a run-up in oil price from $50 to $145 per barrel. An issue for world oil spare capacity is the internal consumption of OPEC producers. OPEC production has ranged between 30 and 33 mbpd since 2004. Internal use is currently about 25% of total OPEC production, but it is growing by 2% per year. The internal consumption growth is largely for nonelastic end uses such as electricity generation, water treatment, and new buildings. If the current world spare capacity is 2 mbpd and the OPEC total production does not increase beyond 33 mbpd, how many years will it take for the spare capacity to fall below 1 mbpd again?