“…In order to quantify the price impact and hence the trading costs, the trader needs a good estimation of G and λ. Some estimators for discrete-time versions of the model were proposed in [8,16,44,45] and in Chapter 13.2 of [9], where only a finite amount of values {G(t n )} N n=1 are estimated for a predetermined grid 0 ≤ t 1 < ... < t n . However, even in this finite dimensional projection of the problem, the convergence of the estimators remains unproved, hence rigorous results on the estimation of G are considered as a long-standing open problem.…”