AH Premium: A Tale of "Siamese Twin" Stocks

57 Pages Posted: 12 Nov 2020 Last revised: 8 Jan 2024

See all articles by Renbin Zhang

Renbin Zhang

Shandong University

Tongbin Zhang

Shanghai University of Finance and Economics

Date Written: October 8, 2023


A large portion of the Chinese twin stocks is traded both in the Shanghai (A-share) and Hong-Kong (H-share) markets. The A- and H-shares are different assets since they can not be exchanged one-to-one. A-shares have sold at a premium: the AH premium. This premium is large (20-50%) and persistent, it has been present since the two markets were connected in Nov 2014 until now. Since both shares pay the same dividends and traders can operate on both markets this provides a natural experiment to test asset pricing models. We show that various standard RE and Bayesian RE asset pricing models cannot explain the AH premium, but a model of internally rational learning where agents learn about stock prices provides a natural explanation. This emphasizes the importance of modeling investors who learn about equity prices. The premium survives the introduction of convergence traders: those who bet on the AH premium going to zero are highly likely to suffer big losses.

Keywords: AH Premium, Learning about Prices, Convergence Trading

JEL Classification: G12, G15

Suggested Citation

Zhang, Renbin and Zhang, Tongbin, AH Premium: A Tale of "Siamese Twin" Stocks (October 8, 2023). Available at SSRN: https://ssrn.com/abstract=3695854 or http://dx.doi.org/10.2139/ssrn.3695854

Renbin Zhang

Shandong University ( email )

shanda nanlu 27
jinan, Shandong 250100

Tongbin Zhang (Contact Author)

Shanghai University of Finance and Economics ( email )

777 Guoding Road
Shanghai, AK Shanghai 200433

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