The United States consumes roughly 23 trillion cubic feet (TCF) of gas per year. About 4 TCF are imported, and 3.5 TCF of that is from Canada. The remained comes in as Liquified Natural Gas (LNG) in ocean-going tankers, from Trinidad and elsewhere. So if we have 238 TCF of domestic reserves and produce 19 TCF in the U.S., we have a 12.5 year supply of proved reserves. That number stays pretty stable as new drilling converts resources to reserves about as fast as the reserves are consumed. The resource estimate indicates that we should be able to keep doing that for another 100 years or so, at the current pattern of consumption and domestic production.