Economic Policy Review

TBA Trading and Liquidity in the Agency MBS Market

Volume 19, Number 1May
JEL classification: G12, G19, G21

Authors: James Vickery and Joshua Wright

Mortgage-backed securities in the United States are generally traded on a “to-be-announced,” or TBA, basis. The key feature of a TBA trade is that the identity of thesecurities to be delivered to the buyer is not specified exactly at the time of the trade, facilitating a liquid forward market. This article describes the main features of the TBA market. It also presents evidence on the liquidity of this market during the financial crisis period. Using variation in TBA eligibility rules, the authors’ estimates suggest that the liquidity benefits associated with the TBA market are of the order of 10to25basis points during 2009and2010, and magnified during periods of market stress. The estimates further suggest that the presence of a government credit guarantee alone does not appear to be sufficient explanation for the liquidity of agency MBS.

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