When she finished with ten minutes to spare, she leaned back. The student next to her was still erasing furiously.
So she did what any desperate HL student would do: she opened the creaking drawer of her desk, pulled out a thick, dog-eared folder, and began looking into IB Econ past papers.
She wrote steadily. Diagrams first. Then definitions. Then real-world examples: carbon taxes in Sweden, sugar taxes in Mexico. For evaluation, she used the “depends on” framework: “The effectiveness depends on the elasticity of demand, the presence of merit good alternatives, and the government’s ability to enforce the tax.”
She began to sketch. Demand and supply curves. A vertical wedge for the tax. The shrinking of consumer and producer surplus. And there it was—the Harberger triangle. Deadweight loss. Not just a term from a glossary, but a real loss of total welfare. She labeled everything: Pc for consumers, Pp for producers, Qt for quantity after tax, Qe for equilibrium.
She grabbed a blank sheet of paper and set a timer for 45 minutes.
Maya highlighted the article like a surgeon. She underlined: “Farmers are switching to durian production.” That was opportunity cost. “Global demand for robusta beans has surged.” That was a demand shifter. The calculation? 12% price increase, 8% quantity decrease. PED = -0.67. Inelastic.
When the timer buzzed, her hand was cramped, but her confidence was not. She compared her answer to the markscheme. She had missed one key point: the role of cross-elasticity of demand for substitutes. A point lost, but a lesson learned.
