内部化外部性：水力压裂的披露监管，钻井活动与水质（WP2022）

题目：Internalizing Externalities: Disclosure Regulation for Hydraulic Fracturing, Drilling Activity and Water Quality

摘要：The rise of shale gas and tight oil development has triggered a major debate about hydraulic fracturing (HF). In an effort to mitigate risks from HF, especially with respect to water quality, many U.S. states have introduced disclosure mandates for HF wells and fracturing fluids. We use this setting to study whether targeting activities with dispersed environmental externalities with disclosure regulation reduces their environmental impact. We find significant improvements in water quality, examining salts that are considered signatures for HF impact, after the disclosure mandates are introduced. We document effects along the extensive and the intensive margin, though most of the improvement comes from the latter. Supporting this interpretation, we find that, after the disclosure mandates, operators pollute less per unit of production, use fewer toxic chemicals, and cause fewer spills and leaks of HF fluids and wastewater. We also present evidence that disclosure enables public pressure, which facilitates internalization.

1.主要故事

基于各州引入对于页岩气、致密油的水力压裂开采方法的披露监管这一场景，采用错层DID/渐进DID方法，检验这种披露监管的Real effects，主要focus对于水质的影响。发现相较于没有采用HF州，采用HF的州在相关披露监管后比披露监管后水质得到了提升。文章进一步探究这种改变来源于Extentive Margin（需要加强披露后减少钻井数量）还是Intensive Margin（降低per-well的污染水平），实证检验发现主要是来自于Intensive Margin。最后，文章还进一不检验了公众压力发挥的作用，披露监管可能导致利益相关者（环保组织，当地社区）对于钻井活动的关注度，从而影响HF运营商的行为。确实发现，受到更多公众关注的HF运营商，披露监管所带来的影响更大。

2.重要Tests

（1）Main Results

（2）Placebo Analyses

Two “placebo” tests. First, we examine changes in the concentration of analytes that are not specific to HF water impact and unlikely to be directly affected by HF activity.

Second, we examine changes in the four HF-specific ion concentrations around the disclosure mandates, but in watersheds with conventional drilling

（3）Extensive and the Intensive Margin（P26）

The evidence provided so far points to an increase in water quality after the introduction of the disclosure mandates. We now turn to examine through which margin such an effect occurs.

This increase in water quality may come from less HF activity in the post-disclosure period relative to the pre-disclosure period (extensive margin) and/or from HF operators shifting to a less-water polluting technology (intensive margin).

Over the two margins, we obtain that around 89 percent of the decrease comes from the intensive margin.(P29)

（4）Analyses of the Changes in HF Operators’ Practices

 First, we examine whether the decline in water impact per new HF well comes at the expense of less productive wells after the disclosure mandates.

Second, we examine whether HF operators start to employ less hazardous chemicals in the post-disclosure period.

Third, we examine the effect of the disclosure regulation on the probability of HF-related incidents.

Our last set of analyses explore the role of public pressure in making disclosure regulation effective. As discussed earlier, a likely channel is that disclosure regulation enables public pressure from local environmental groups, local communities and the general public on HF operators