Drilling 1 Economic welfare 1 Environmental quality 1 Environmental regulations 1 Firm exit 1 Fixed cost Infill drilling 1 Montana 1 North Dakota 1 Oil and gas 1 Oil and gas regulation 1 Policy makers 1 Resource development 1 Shale oil 1 United States 1 cost analysis 1 drilling 1 environmental policy 1 environmental quality 1 firm size 1 hypothesis testing 1 oil production 1 oil shale 1 regulatory approach 1 resource development 1