Polarised growth models predict that factors of production move in the same direction. More important, these models predict that income disparities between regions will grow as a result of factor migration. It's not hard to figure out why a region that loses labor and capital eventually experiences a fall in average wages. These models demonstrate the Keynesian income multiplier in a direct fashion. Suppose that the biggest company in your home town were to close down.
Industrial clusters tend to be highly export-oriented.
If we were to calculate LQs for employment in the medical instruments sector, for instance, then Western New York would show up alongside southern Florida and southern California as a region that contains an above average concentration of this type of industrial production. The simplest version of the LQ is calculated by dividing regional employment in a specific sector by total regional employment, and then dividing that ratio by national employment in the same sector over total national employment.