“…Fisher and Fleissig (1997, pp. 461-464) divided their dataset (also from Thornton and Yue, 1992) into 21 subsamples of 1960:1-1993:5 and they tested groups of monetary assets (corresponding to M1A, M1, M2, M3, and L) for weak separability over each of them. Weak separability is the key property required for the existence of an economic monetary aggregate, see Barnett (1982), Swofford and Whitney (1994), and Barnett and Serletis (2000).…”