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Unraveling Limit Order Books Using Just Bid/Ask Prices

How much of the structure of a Limit Order Book (LOB) can be recovered by only observing the trade and quote (TAQ) sequence? In this paper we study the queueing dynamics in the LOB which, surprisingly, allows us to recover the LOB of stocks having relatively large spread with reasonable empirical accuracy. In particular, we are able to estimate the time-average order depth on almost all price levels of interest in the LOB by observing only the bid/ask price at the times of trades. As applications, we can use the result to estimate the price impact of trades and size of hidden orders. Our approach starts from a Markovian queueing model for the LOB dynamics. We apply a multi-scale analysis on the model to obtain a closed-form expression connecting the trade price change distribution and the LOB structure, which enables the recovery of LOB from the TAQ sequence. Our approach is also applicable to extended models with autocorrelated and state-dependent order ows in the LOB.