“…is to estimate technical efficiency from Silva & Oude Lansink's (2013) dynamic directional distance function (oriented in the space of freely-varying inputs and investments into quasi-fixed dynamic factors) under its duality to the optimal current value function associated with the firm's intertemporal cost-minimization problem under the Hamilton-Jacobi-Bellman conditions (e.g., Serra et al, 2011;Kapelko et al, 2014;Oude Lansink et al, 2015;Kapelko, Oude Lansink & Stefanou, 2016, 2017Minviel & Sipiläinen, 2018). Thus, in practice, the strategy for a (primal) estimation of dynamic technical efficiency is effectively the same as that for the estimation of a more conventional static efficiency except that in the former case a distance to the frontier is measured in the space of variable inputs and investments as opposed to merely conditioning the distance function on quasi-fixed levels of dynamic inputs.…”