This paper studies nonstationarities in panels of exchange rates and interest rates. For this, we survey developments in the analysis of nonstationary panels with cross-sectional dependence modeled as a factor model. We focus on panel unit root tests and on inference on the nonstationary...

We propose new methods for estimating the bid-ask spread from observed transaction prices alone. Our methods are based on the empirical characteristic function instead of the sample autocovariance function like the method of Roll (1984). As in Roll (1984), we have a closed form expression for...