No, not at this point. On a semi-annual basis we do an evaluation of the upstream footprint of natural gas, because there's a lot of research and there's a lot of stuff in the news around the greenhouse gas footprint around unconventional gas.
In collaboration with the U.S. DOE and with NRCan, we do a scientific study that goes into their models for actually determining the greenhouse gas footprint of the fuel as it goes into the vehicle. We haven't seen a dramatic change in the upstream footprint of that gas such that it's going to negatively impact our greenhouse gas emission reductions at the tailpipe. The bulk of greenhouse gas emissions from a vehicle occur at combustion. Once the fuel is already on board, the bulk of the greenhouse gas emissions emerge when it gets used.