4.4. Changes in the interregional nodal accessibility of Southeast Asian hubs The proliferation of linkages in the international economy implies that an effective hub will have nonstop connections to dozens of cities around the world. Accordingly, the interregional centrality of the five Southeast Asian hubs was measured using a first order (i.e., nonstop) adjacency matrix examining the linkages between (1) the five main hubs of the region and (2) a selection of 48 important business destinations within the nonstop range of at least one Southeast Asian hub in 1997 (Table 8).