  We carry out a detailed large-scale data analysis of price response functions
in the spot foreign exchange market for different years and different time
scales. Such response functions provide quantitative information on the
deviation from Markovian behavior. The price response functions show an
increase to a maximum followed by a slow decrease as the time lag grows, in
trade time scale and in physical time scale, for all analyzed years.
Furthermore, we use a price increment point (pip) bid-ask spread definition to
group different foreign exchange pairs and analyze the impact of the spread in
the price response functions. We find that large pip spreads have a stronger
impact on the response. This is similar to what has been found in stock
markets.
