International Lecture on Economics by Dr. Roperto S. Deluna, Jr. last September 21, 2026 with Universitas Diponegoro Students

Key Outcomes

A guest lecture on foundational economics was delivered by Dr. Rupert (De Luna) from the University of Southeastern Philippines (USeP) to approximately 35 business administration students at Happy University (Indonesia). The session covered demand and supply theory, market equilibrium, elasticity, externalities, and circular economy concepts — all framed through a sustainable business lens. The lecture ran approximately one hour with a brief Q&A at the close.

Session Setup

• Host/Moderator: Ray (student co-host); Dr. Vicky (Robetmi) presided over opening
• Guest Speaker: Dr. Rupert De Luna, USeP Davao City
• Facilitator: Jennifer (USeP-College liaison, former Korea study connection)
• Co-hosts assigned: Ivan, Ray, and Russell (Rasendriya) 12
• Jennifer noted the session is part of USeP's ARISE program (Academic Research and International Society Exchange), with intent for future COIL (Collaborative Online International Learning) activities 3

Core Economics Concepts Covered

Demand

• Law of Demand: Price rises → quantity demanded falls (ceteris paribus) 4
• Two mechanisms: substitution effect (buyers switch to alternatives) and income effect (real purchasing power falls) 5
• Distinction emphasized: change in quantity demanded (movement along curve, own-price change) vs. change in demand (curve shift from income, preferences, related goods prices, expectations, number of buyers) 67
• Giffen/luxury goods noted as exception but excluded from typical household market basket analysis 8

Supply

• Law of Supply: Price rises → quantity supplied rises (ceteris paribus); supply curve slopes upward because marginal costs rise 910
• Supply shifters: input prices, technology, weather/natural events, expectations, policy/number of sellers 1011
• Supply curve represents the firm's marginal cost curve 10

Elasticity

• Inelastic demand → price increases raise total revenue; elastic demand → price increases reduce revenue 1213
• Fuel/energy demand is inelastic in the short run — factories and commuters cannot switch overnight 1415
• Key rule: know your elasticity before adjusting price 13

Market Equilibrium & Comparative Statics

• Equilibrium: quantity demanded = quantity supplied; no shortage, no surplus, no incentive to change 16
• Three-step comparative statics framework: (1) identify shock and which curve it hits, (2) determine shift direction, (3) read the new equilibrium price and quantity 1718
• Example applied: 90% technology cost reduction in solar → supply shifts right → price falls, quantity rises 18

Sustainability & Market Failure

• Core thesis: "Prices allocate resources; most sustainability problems start with a price that is wrong or missing." 19
• Negative externality: Producer externalizes costs (e.g., pollution, plastic waste) → market price too low, quantity too high → deadweight loss 20
• Fix: Pigouvian tax or permit priced equal to external cost forces producers to internalize social cost; output moves from over-production toward socially optimal quantity 21
• Tragedy of the Commons: Resources without price are overused; no market mechanism to correct 22
• Burden of tax/subsidy falls on the inelastic side of the market (typically consumers for fuel/energy) 23

Circular Economy & Extended Producer Responsibility (EPR)

• Circular economy keeps materials at highest value vs. linear "make–use–dispose" model 24
• Barrier: virgin materials are artificially cheap because environmental costs are excluded from price 24
• Philippines EPR Act (2022): Large firms must recover ≥60% of plastic footprint annually; >1,000 enterprises registered; early targets exceeded 25
• Indonesia: 30% plastic reduction target by 2029; several regions have banned single-use plastics 26
• Dr. Rupert's current research focuses on circular transition barriers and behavioral economics; open to student collaboration 26

Key Takeaways for Business Leaders

1. Prices = signals, not just costs — read them as information about scarcity 22
2. Sustainability problems are price problems — wrong price or no price at all 22
3. Policy is repricing — carbon borders, EPR, disclosure rules turn externalities into real cost lines 27
4. Competitive advantage goes to firms that read demand/supply shifts early and price them first 2728
5. Poverty and inequality are structural barriers to sustainability adoption in both Philippines and Indonesia 27
6. Ethical producers should internalize externalities; conscious consumers reinforce this through purchasing behavior 21

Action Items & Follow-Up

• Students: Complete the attendance/feedback form shared during the session 29
• Dr. Rupert: Open to follow-up lectures on specific topics and research collaboration (circular economy, resource economics) 29
• Ray/Team: Shared Dr. Rupert's PowerPoint with students for independent review 29
• Future collaboration discussed, including potential offline/in-person engagement between the two universities 29