The filtering of wealth from central, prosperous areas, to peripheral, needier areas. The spread effect is the spatial equivalent of trickle-down economics. Spread-backwash effects were outlined by G. Myrdal (1957) and A. Hirschman (1959) in the late 1950s. ‘Generally, spread effects are the positive effects of urban proximity for communities, and backwash effects are the negative consequences of proximity. According to Hirschman, the most important spread effect is the purchase and investments of the affluent region in the outlying region’ (Ganning 2010).