“…These unintended transfers, where the owners of such knowledge cannot prevent others from making use of it (Grossman and Helpman, 1991, pp. 15-16), include: departure of key scientists and engineers (including poaching of key staff); informal know-how sharing (von Hippel, 1987Hippel, , 1990; unintended signalling of key information at conferences and workshops; membership of 'invisible colleges' and research schools (Olesko, 1993, p. 16) and professional links associated with speci c 'communities of practice' (Lave and Wenger, 1991;Barley, 1996) related to membership of professional associations or informal groupings (see, for example, Sørensen and Levold, 1992); and unintended leakage by consultants or design practices of information picked up from one client and applied to others.…”