Classwork 4
Designing Rules for a Shared Aquifer
Four farms draw groundwater from the same aquifer. Pumping more water can raise one farm’s crop revenue today, but it lowers the water table and raises future pumping costs for every farm.
The county is considering new rules for pumping and a public groundwater-monitoring program. Your job is to diagnose the incentives before recommending an institution.
Task 1 · Identify the resources
For each resource below, decide whether its use is rival and whether users are excludable. Then name the type of good or resource.
- Groundwater in the aquifer: water pumped by one farm is no longer available to the other farms. Without meters or enforceable rules, it is difficult to prevent a nearby farm from pumping.
- A county groundwater report: after the report is posted online, one person’s use does not reduce what others can learn from it, and anyone can read it.
Then answer these questions:
- Is calling the aquifer a common-pool resource a statement about its physical characteristics, its governance, or both?
- Why are common property and open access not the same arrangement?
- Groundwater is rival because one farm’s withdrawal leaves less water—or a lower water table—for others. In the stated setting, users are difficult to exclude. The aquifer is therefore a common-pool resource.
- The report is nonrival because many people can use the same information, and it is difficult to exclude people once the report is public. It is a public good.
- “Common-pool resource” describes the resource’s economic characteristics: rivalry and difficulty of exclusion. It does not by itself tell us who owns the resource or what rules govern it.
- Common property has a defined group with rules for access and use. Under open access, no person or group exercises effective exclusion. A common-pool resource can be governed under either arrangement.
Task 2 · Read the pumping incentive
Each farm simultaneously chooses Regular pumping or Extra pumping. Choosing Extra means pumping one additional acre-foot.
- Extra pumping gives the farm that chooses it $30 in additional crop revenue.
- Each extra acre-foot creates $10 in next-season pumping costs for each of the four farms, including the farm that pumped it.
- Treat all other revenues and costs as unchanged.
- Suppose the other farms’ choices are fixed. If your farm switches from Regular to Extra:
- How much additional revenue does your farm receive?
- How much additional future cost does your farm bear?
- What is the net change in your farm’s own payoff?
- Based on that private payoff, which choice will each farm be tempted to make?
- Complete the table for the four farms together.
| Farms choosing Extra, N | Total extra crop revenue | Total drawdown cost | Change in the four farms’ combined payoff |
|---|---|---|---|
| 0 | |||
| 1 | |||
| 2 | |||
| 3 | |||
| 4 |
- Does one more Extra choice increase or decrease the four farms’ combined payoff? What outcome is socially efficient?
- Of the $40 total drawdown cost caused by one farm’s Extra choice, how much is an external cost to the other farms?
- Explain in one or two sentences why the private incentive and the socially efficient outcome differ.
- The switch gives the farm $30 in added crop revenue and $10 in added future pumping cost. Its own payoff therefore rises by $20.
- Each farm is privately tempted to choose Extra, regardless of the other farms’ choices.
| Farms choosing Extra, N | Total extra crop revenue | Total drawdown cost | Change in the four farms’ combined payoff |
|---|---|---|---|
| 0 | $0 | $0 | $0 |
| 1 | $30 | $40 | -$10 |
| 2 | $60 | $80 | -$20 |
| 3 | $90 | $120 | -$30 |
| 4 | $120 | $160 | -$40 |
- Every additional Extra choice lowers the four farms’ combined payoff by $10. The socially efficient outcome is therefore for all four farms to choose Regular.
- The pumping farm bears $10 of the $40 cost itself. The remaining $30 imposed on the other three farms is the external cost.
- The pumping farm compares its $30 benefit with only the $10 cost it bears, so Extra looks privately worthwhile. Society compares the same $30 benefit with the full $40 cost across all farms, so Extra reduces total welfare.
Task 3 · Compare three rules
The county considers three arrangements for the same aquifer.
Rule A · Unrestricted basin
Any nearby farm may pump. There is no registry, meter, or enforceable limit.
Rule B · Water-user association
Only registered members may pump. Members vote on a group limit, every well is metered, an elected monitor reports use, and the association applies an agreed penalty when a member exceeds the limit.
Rule C · Individual pumping allowances
The county assigns each farm an enforceable annual allowance. A farm may transfer unused units to another registered farm, and all pumping is metered.
- Complete the institutional diagnosis.
| Question | Rule A | Rule B | Rule C |
|---|---|---|---|
| Who may pump? | |||
| Who can exclude unauthorized users? | |||
| Who monitors and enforces the rule? | |||
| Can an individual transfer a use entitlement? | |||
| Governance regime |
- Which rule or rules have the strongest exclusivity, enforceability, and transferability? Support each choice with one feature of the rule.
- Under which rule is the incentive from Task 2 most likely to remain? Explain.
- A rule written on paper may still fail. Identify one practical condition needed for Rule B or Rule C to work as intended.
| Question | Rule A | Rule B | Rule C |
|---|---|---|---|
| Who may pump? | Any nearby farm | Registered association members | Farms holding county allowances |
| Who can exclude unauthorized users? | No actor effectively does | The association | The county |
| Who monitors and enforces the rule? | No one | Elected monitor and association | County, using well meters |
| Can an individual transfer a use entitlement? | No defined entitlement exists | Not under the stated rule | Yes, among registered farms |
| Governance regime | Open access | Common property | State-defined individual rights |
- Rules B and C both have much stronger exclusivity and enforceability than Rule A because they define authorized users, measure pumping, and specify enforcement. Rule C has the strongest stated transferability because allowances may move between registered farms. The information given does not establish that B or C must enforce more successfully in practice.
- The Task 2 incentive is most likely to remain under Rule A because each farm can capture its private benefit while no effective limit makes it face the full shared cost. The incentive can also persist under Rule B or C if monitoring or enforcement is weak.
- Examples include accurate meters, a monitor with enough resources, a penalty large and certain enough to matter, clear basin boundaries, timely data, or users who view the rule as legitimate.
Task 4 · Provide groundwater information
The county can publish up to three groundwater reports per year. Each report costs $40. The table gives each beneficiary’s marginal willingness to pay for one additional report.
| Additional report | Farm A | Farm B | Town residents | Social marginal benefit |
|---|---|---|---|---|
| 1st | $30 | $20 | $20 | |
| 2nd | $20 | $15 | $15 | |
| 3rd | $10 | $5 | $5 |
- Why do we add the three marginal benefits vertically for a public report?
- Complete the social-marginal-benefit column.
- How many reports are efficient? Use the marginal rule: provide another report while its social marginal benefit is at least its marginal cost.
- What is the total net benefit from the efficient number of reports?
- Why might voluntary donations provide fewer reports than the efficient number?
- Suggest one way to finance the reports. State one advantage and one distributional concern.
- Every beneficiary receives the same report. At each quantity, we add how much all beneficiaries value that shared unit rather than adding separate quantities.
| Additional report | Farm A | Farm B | Town residents | Social marginal benefit |
|---|---|---|---|---|
| 1st | $30 | $20 | $20 | $70 |
| 2nd | $20 | $15 | $15 | $50 |
| 3rd | $10 | $5 | $5 | $20 |
The efficient quantity is two reports. The first and second reports have social marginal benefits of $70 and $50, both at least the $40 marginal cost. The third report’s $20 benefit is below its $40 cost.
Total net benefit is
(\$70-\$40)+(\$50-\$40)=\boxed{\$40}.
Once a report is posted, people can benefit even if they do not contribute. Each person may wait for others to pay, so voluntary funding can fall short despite a combined benefit above cost.
One option is a county-wide tax. It reliably shares the cost and can fund the efficient quantity, but equal payments may be viewed as unfair when benefits or ability to pay differ. A well fee or benefit-based charge has different efficiency and equity trade-offs.
Exit sentence
Complete this sentence in one or two lines:
A shared natural resource is more likely to be conserved when an institution makes resource users __________ because __________.
A shared natural resource is more likely to be conserved when an institution makes resource users bear more of the costs their withdrawals impose on others because doing so reduces their incentive to overuse the resource.