Many past research attempts measured the impact of environmental regulation using data on Pollution Abatement Cost (PAC) (more regulation => more PAC) . Other studies focused on the level of greenhouse gas (GHG) emissions (more regulation => lower emissions).

If I were to use a proxy for the level of regulation today, which data would be more reliable and easier to obtain? In general, are emission data more reliable than data on abatement costs? Is there a current abandonment of PAC?

Regards