药品需求弹性的四象限划分与比较：基于中国医药市场的分析

Abstract

This study uncovers a surprisingly common phenomenon in pharmaceutical markets: 39.9% of drugs exhibit positive price elasticity, meaning that a price decrease leads to lower demand. This pattern directly challenges the presumed universality of the law of demand. Based on market data for 1,006 drugs in China from 2019 to 2024, combined with drug-specific academic knowledge indexed via Google Scholar, we provide the first systematic documentation and explanation of this empirical “anomaly.” We propose an innovative four-quadrant analytical framework that classifies drugs according to the direction (positive/negative) and intensity (strong/weak) of their price elasticity, revealing distinct underlying market equilibrium mechanisms. The first quadrant (strong positive elasticity, ε>1, accounting for 15.5% of the sample) reflects extreme quality uncertainty, where price primarily serves as a quality signal. The second quadrant (weak positive elasticity, 0<ε<1, 24.4%) represents a transitional market where price signaling begins to emerge. The third quadrant (weak negative elasticity, -1<ε<0, 37.8%) demonstrates demand rigidity under limited competition. The fourth quadrant (strong negative elasticity, ε<-1, 22.3%) exhibits a healthy competitive market consistent with traditional demand theory.
A key finding is that the accumulated academic literature on a drug, used as a proxy for its clinical value, substantially shapes its price elasticity: a 1%increase in literature volume reduces the absolute value of elasticity by 0.07%, and increasing literature volume from the 25th to the 75th percentile (approximately from 1,100 to 73,000 articles) reduces price sensitivity by roughly 30%. This relationship follows an inverted-U pattern, with a turning point around 44,000 publications. The effects of market structure are unexpected: an increase in the number of approved competitors does not enhance price sensitivity; instead, it reduces the absolute elasticity and increases the likelihood of positive elasticity, revealing a mechanism of market failure in which “excessive competition amplifies quality uncertainty.”
A quasi-natural experiment based on China’s centralized procurement policy further validates the four-quadrant framework. Drugs with negative elasticity behave as expected under price cuts and achieve “price-for-volume” outcomes, whereas drugs with positive elasticity experience “winning the bid but losing the market,” as steep price reductions are interpreted as signals of compromised quality.
The theoretical contributions of this study are threefold. First, it provides large-scale evidence showing that the law of demand systematically breaks down in markets characterized by extreme information asymmetry. Second, it establishes a conceptual link between the accumulation of scientific knowledge and the formation of market demand. Finally, it demonstrates the complex equilibrium that emerges when price plays a dual role, functioning simultaneously as a budget constraint and as a signal of product quality.
The policy implications are substantial. Uniform price interventions may generate counterproductive effects, making it necessary to design differentiated pricing and procurement strategies based on drug-specific elasticity characteristics. Public investment in scientific research plays a stabilizing role in markets, particularly in areas with insufficient knowledge accumulation. Ultimately, improving market efficiency requires a more robust information infrastructure. This study provides a new lens for understanding information-intensive markets and offers important insights for pharmaceutical policy design and research on other professional service sectors.

Date of Award	4 Oct 2025
Original language	Chinese (Simplified)
Awarding Institution	China Europe International Business School
Supervisor	Wei Guo (Supervisor) & Bala Ramasamy (Supervisor)