A formal game whereby, on choosing a particular strategy, one competitor’s gain is his opponent’s loss. Liard-Muriente (2007) Area 39, 2 writes that ‘regional development policies could be described as a zero-sum game, with local job reshuffling as the outcome. After all, if one area accomplishes growth, it will be at the expense of another area. Thus, overall welfare is unchanged.’ Polèse and Shearmur (2006) Papers Reg. Sci. 85, 1 agree: ‘stable national populations means a zero-sum demographic game for interregional systems…Assuming (as most migration models do), that population movements largely follow the spatial distribution of economic opportunities, the key factor becomes the spatial distribution of employment. In such an environment, if shifts in employment continue, on balance, to favour the centre over the periphery, the latter must decline.’