Main Point
A tool can replace one activity while making another contribution more useful. Follow the complete service, then multiply effort per accepted unit by volume to examine the consequences for total work and people.
Key Points
- Substitution and complementarity describe relationships within a particular process and can operate together.
- The boundary of automation depends on tested reliability, acceptance and the service setting.
- Lower effort per response can accompany either lower total effort or a larger service using more total effort.
- Demand, capacity and organizational choices connect a technical change to access, staff work and resource use.
1. A Visitor Request Reveals Two Relationships
In an imagined community museum, Rosa asks for a short visit route with places to sit for her father. An assistant prepares wording from approved information. Leela, the visitor adviser, checks a temporary closure, asks about their interests and adjusts the route. The museum wants to widen access to planning support; staff want to understand how their work changes.
Substitution means a capability replaces some use of another input under the relevant conditions. Here the assistant can replace some initial wording activity. Complementarity means it increases another input's usefulness or productivity. A useful draft can help Leela apply her visitor knowledge to a suitable plan. Analyze these relationships at the level of the actual task and contribution.
The museum also tests routine opening-time answers. Reliable current information and acceptable delivery could allow more of that service to be automated. Route planning brings different preferences and exceptions. Test each boundary as the system and users change.
2. What A Workplace Design Shows
In the published 2025 *Generative AI at Work* study, a system suggested replies during customer-support conversations. Agents could edit or ignore suggestions and remained responsible for the conversation. The researchers measured issues resolved per hour in one firm's workflow. This is a concrete assistance design to examine; its setting and period remain attached to the study. Lesson 4 examines workplace findings and comparisons further.
For the museum, compare the complete interaction: which activity does the tool perform, and what happens to the adviser's contribution and the accepted visitor result?
3. The Director's Decision Requires A Volume Assumption
Suppose a trial verifies lower total labor per accepted planning response at the same service standard. The director can keep the scale, offer the service more widely or assign time to difficult visits. Demand describes the amount people want to use; service provision also depends on the museum's decisions and capacity.
The following figures are supplied for the fictional museum:
| Scenario | Accepted responses | Labor minutes per response | Total labor minutes |
|---|---|---|---|
| Original service | 12 | 30 | 360 |
| Redesigned, same volume | 12 | 20 | 240 |
| Redesigned, expanded volume | 24 | 20 | 480 |
Total labor = accepted responses × complete labor per response.
At fixed volume the process releases 120 minutes. At 24 responses it uses 120 more minutes than the original service, while each response still needs less effort. The different volume assumption explains the different totals.
4. Investigate Whether The Service Expands
An easier request process, lower price or more useful response can attract additional use. Museum outreach could help people consider a visit. Actual request and visitor records would test that possibility. Transport, limited need or staff capacity could constrain it.
At fixed volume the director could assign released time to personal assistance or reduce scheduled work. With expanded use, staff could serve more people and handle a different case mix. Training and funding affect whether that expansion is practical. Staff and community groups can shape the service decision. Record actual provision, roles, hours and hiring to understand what happens.
Computing charges and energy need their own units and records. For each measured resource, examine use per response and response volume. Explaining pay or employment additionally requires budgets, hiring, hours and organizational decisions.
5. Resolve The Museum's Question
The assistant can change wording activity and the use of adviser expertise at the same time. Test the service boundary, measure the complete accepted response and investigate actual demand. The museum can then compare a fixed-volume use of released capacity with a funded expansion of access. You can explain why a faster activity leaves several possible paths and identify the evidence that distinguishes them.
The next step is judging evidence that a new process works. Lesson 4 examines workplace studies and the comparisons behind their findings.
6. Learning Check — M31-L03-Q01
Why analyze both task effort and demand? Explain how lower effort per unit can coexist with greater total work. State what must be checked before describing employment or resource-use outcomes. Give your answer before consulting the separate key.
7. Practice — M31-L03-P01
Use the distinct fictional support-desk worksheet. Calculate original workload and the faster process at two supplied volumes. Identify possible substitution and complementarity and evidence that would test demand. Response fields remain blank for your attempt; the key is separate.
Sources
Erik Brynjolfsson, Danielle Li and Lindsey Raymond, *Generative AI at Work*, *The Quarterly Journal of Economics*, 140(2), May 2025, pp. 889–942; published online 4 February 2025 by Oxford University Press. Introduction describes the suggestion system, agent responsibility and edit/ignore choice. Staggered workplace rollout began in fall 2020 and winter 2021; publication date is distinct from the workplace event period. The study's medium-run single-firm evidence supplies the design example used here; aggregate employment or wage effects are outside its observed scope.
Published primary article reopened 25 October 2026. The museum and support-desk calculations are fictional teaching scenarios. They supply no measured demand, staffing or energy forecast.