This supplemental appendix extends the main paper by presenting additional analyses and robustness checks. It also describes the procedure to construct the Monthly TAQ effective spread benchmark.The paper "A Simple Estimation of Bid-Ask Spreads from Daily Close, High, and Low Prices" to which...

We propose a new method to estimate the bid-ask spread when quote data are not available. Compared to other low-frequency estimates, this method utilizes a wider information set, namely, readily available close, high, and low prices. In the absence of end-of-day quote data, this method generally...